How do I check if a string contains a specific word

Question

Consider    a    How are you     if   a contains  are       echo  true     Suppose I have the code above  what is the correct way to write the statement if   a contains  are

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Here is a little utility function that is useful in situations like this     returns true if  needle is a substring of  haystack function contains  needle   haystack        return strpos  haystack   needle      false

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The strpos function works fine  but if you want to do case-insensitive checking for a word in a paragraph then you can make use of the stripos function of PHP   For example    result   stripos  I love PHP  I love PHP too     php    if   result     false           Word does not exist   else          Word exists     Find the position of the first occurrence of a case-insensitive substring in a string   If the word doesn t exist in the string then it will return false else it will return the position of the word

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You should use case Insensitive format so if the entered value is in small or caps it wont matter    lt  php  grass    This is pratik joshi    needle    pratik   if  stripos  grass  needle      false         If i EXCLUDE       false then if string is found at 0th location      still it will say STRING NOT FOUND as it will return  0  and it          will goto else and will say NOT Found though it is found at 0th location        echo  Contains word    else      echo  does NOT contain word       gt    Here stripos finds needle in heystack without considering case  small caps    PHPCode Sample with output

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You can also use built-in functions strchr   and strrchr   and extensions for multibyte strings mb strchr   and mb strrchr     These functions return parts of strings  and FALSE if nothing is found    strchr   - Find the first occurrence of a string  is an alias of strstr      strrchr   - Find the last occurrence of a character in a string

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Make use of case-insensitve matching using stripos     if  stripos  string  stringToSearch      false        echo  true

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It can be done in three different ways     a    How are you      1- stristr     if  strlen stristr  a  are    gt 0        echo  true      are Found       2- strpos     if  strpos  a   are       false       echo  true      are Found      3- preg match     if  preg match  are   a      1       echo  true      are Found

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Lot of answers that use substr count checks if the result is  gt 0  But since the if statement considers zero the same as false  you can avoid that check and write directly   if  substr count  a   are        To check if not present  add the   operator    if   substr count  a   are

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Maybe you could use something like this    lt  php     findWord  Test all OK         function findWord  text            if  strstr  text   ok                  echo  Found a word                     else                       echo  Did not find a word                     gt

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Do not use preg match   if you only want to check if one string is contained in another string  Use strpos   or strstr   instead as they will be faster   http   in2 php net preg match   if  strpos  text   string name       false      echo  get the string

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I think that a good idea is to use mb stpos    haystack    How are you     needle    are    if  mb strpos  haystack   needle      false         echo  true       Because this solution is case sensitive and safe for all Unicode characters     But you can also do it like this  sauch response was not yet    if  count explode  needle   haystack    gt  1         echo  true       This solution is also case sensitive and safe for Unicode characters   In addition you do not use the negation in the expression  which increases the readability of the code     Here is other solution using function   function isContainsStr  haystack   needle         return count explode  needle   haystack    gt  1     if  isContainsStr  haystack   needle          echo  true

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Using strstr   or stristr   if your search should be case insensitive would be another option

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if  preg match    are      a        echo  true

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If you want to check if the string contains several specifics words  you can do    badWords   array  dette    capitale    rembourser    ivoire    mandat      string    a string with the word ivoire     matchFound   preg match all    b     implode  badWords           b i    string   matches    if   matchFound        echo  a bad word has been found     else       echo  your string is okay       This is useful to avoid spam when sending emails for example

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To determine whether a string contains another string you can use the PHP function strpos     int strpos   string  haystack   mixed  needle    int  offset   0       lt  php   haystack    how are you    needle    are    if  strpos  haystack  needle      false        echo   haystack contains  needle        gt    CAUTION   If the needle you are searching for is at the beginning of the haystack it will return position 0  if you do a    compare that will not work  you will need to do a      A    sign is a comparison and tests whether the variable   expression   constant to the left has the same value as the variable   expression   constant to the right    A     sign is a comparison to see whether two variables   expresions   constants are equal AND have the same type - i e  both are strings or both are integers

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Look at strpos      lt  php      mystring    abc        findme      a        pos   strpos  mystring   findme           Note our use of      Simply     would not work as expected        because the position of  a  was the 0th  first  character      if   pos     false            echo  The string   findme  was not found in the string   mystring               else           echo  The string   findme  was found in the string   mystring             echo   and exists at position  pos            gt

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Check if string contains specific words    This means the string has to be resolved into words  see note below    One way to do this and to specify the separators is using preg split  doc     lt  php  function contains word  str   word         split string into words      separators are substrings of at least one non-word character    arr   preg split    W      str  NULL  PREG SPLIT NO EMPTY         now the words can be examined each   foreach   arr as  value        if   value      word          return true              return false     function test  str   word      if  contains word  str   word         echo  string       str      contains word       word      n       else       echo  string       str      does not contain word       word      n            a    How are you     test  a   are    test  a   ar    test  a   hare       gt    A run gives    php -f test php                    string  How are you   contains word  are   string  How are you   does not contain word  ar  string  How are you   does not contain word  hare    Note  Here we do not mean word for every sequence of symbols   A practical definition of word is in the sense the PCRE regular expression engine  where words are substrings consisting of word characters only  being separated by non-word characters      A  word  character is any letter or digit or the underscore character    that is  any character which can be part of a Perl   word    The   definition of letters and digits is controlled by PCRE s character   tables  and may vary if locale-specific matching is taking place

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Another option is to use the strstr   function  Something like   if  strlen strstr  haystack  needle   gt 0       Needle Found     Point to note  The strstr   function is case-sensitive  For a case-insensitive search  use the stristr   function

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Use    text    This is a test   echo substr count  text   is       2     So if you want to check if is exists in the text just put    in a condition like this  if  substr count  text   is    gt  0        echo  is exists

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I m a bit impressed that none of the answers here that used strpos  strstr and similar functions mentioned Multibyte String Functions yet  2015-05-08    Basically  if you re having trouble finding words with characters specific to some languages  such as German  French  Portuguese  Spanish  etc   e g                            you may want to precede the functions with mb   Therefore  the accepted answer would use mb strpos or mb stripos  for case-insensitive matching  instead   if  mb strpos  a  are       false        echo  true       If you cannot guarantee that all your data is 100  in UTF-8  you may want to use the mb  functions   A good article to understand why is The Absolute Minimum Every Software Developer Absolutely  Positively Must Know About Unicode and Character Sets  No Excuses   by Joel Spolsky

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Another solution for a specific string    subject    How are you     pattern     are    preg match  pattern   subject   match   if   match 0      are         echo true      You can also use strpos   function

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The function below also works and does not depend on any other function  it uses only native PHP string manipulation  Personally  I do not recommend this  but you can see how it works    lt  php  if   function exists  is str contain        function is str contain  string   keyword          if  empty  string     empty  keyword   return false       keyword first char    keyword 0        keyword length   strlen  keyword        string length   strlen  string           case 1     if   string length  lt   keyword length  return false          case 2     if   string length     keyword length          if   string     keyword  return true        else return false                case 3     if   keyword length    1          for   i   0   i  lt   string length   i                  Check if keyword s first char    string s first char         if   keyword first char     string  i               return true                                  case 4     if   keyword length  gt  1          for   i   0   i  lt   string length   i                         the remaining part of the string is equal or greater than the keyword                    if    string length   1 -  i   gt    keyword length                  Check if keyword s first char    string s first char           if   keyword first char     string  i                  match   1              for   j   1   j  lt   keyword length   j                    if    i    j  lt   string length   amp  amp   keyword  j      string  i    j                      match                                  else                   return false                                             if   match     keyword length                  return true                                end if first match found                           end if remaining part                   else             return false                        end for loop                   end case4            return false          Test   var dump is str contain  test    t       true var dump is str contain  test           false var dump is str contain  test    test       true var dump is str contain  test    testa       flase var dump is str contain  a----z    a       true var dump is str contain  a----z    z       true  var dump is str contain  mystringss    strings       true

User · Answer

You can use the strstr function    haystack    I know programming    needle      know    flag   strstr  haystack   needle    if   flag        echo  true       Without using an inbuilt function    haystack     hello world    needle    llo     i    j   0   while  isset  needle  i          while  isset  haystack  j    amp  amp    needle  i      haystack  j               j             i   0            if   isset  haystack  j              break             i         j       if   isset  needle  i          echo  YES     else      echo  NO

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A simpler option   return     empty  a   amp  amp  strpos  a   are     true   false

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You can use the strpos   function which is used to find the occurrence of one string inside another one   a    How are you     if  strpos  a   are       false        echo  true      Note that the use of     false is deliberate  neither    false nor     true will return the desired result   strpos   returns either the offset at which the needle string begins in the haystack string  or the boolean false if the needle isn t found  Since 0 is a valid offset and 0 is  quot falsey quot   we can t use simpler constructs like  strpos  a   are    Edit  Now with PHP 8 you can do this  if  str contains  How are you    are           echo  true      RFC str contains

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A string can be checked with the below function   function either String existor not  str   character        if  strpos  str   character      false            return true            return false

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The short-hand version   result   false   strpos  a   are

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You could use regular expressions as it s better for word matching compared to strpos  as mentioned by other users  A strpos check for are will also return true for strings such as  fare  care  stare  etc  These unintended matches can simply be avoided in regular expression by using word boundaries  A simple match for are could look something like this   a    How are you     if  preg match    bare b     a         echo  true      On the performance side  strpos is about three times faster  When I did one million compares at once  it took preg match 1 5 seconds to finish and for strpos it took 0 5 seconds  Edit  In order to search any part of the string  not just word by word  I would recommend using a regular expression like  a    How are you     search    are y   if preg match  quot    search  i quot    a         echo  true      The i at the end of regular expression changes regular expression to be case-insensitive  if you do not want that  you can leave it out  Now  this can be quite problematic in some cases as the  search string isn t sanitized in any way  I mean  it might not pass the check in some cases as if  search is a user input they can add some string that might behave like some different regular expression    Also  here s a great tool for testing and seeing explanations of various regular expressions Regex101 To combine both sets of functionality into a single multi-purpose function  including with selectable case sensitivity   you could use something like this  function FindString  needle  haystack  i  word          i should be  quot  quot  or  quot i quot  for case insensitive     if  strtoupper  word    quot W quot              if  word is  quot W quot  then word search instead of string in string search          if  preg match  quot   b  needle  b   i  quot    haystack                          return true                      else               if preg match  quot    needle    i  quot    haystack                          return true                      return false         Put quotes around true and false above to return them as strings instead of as bools ints     One more thing to take in mind  is that  b will not work in different languages other than english  The explanation for this and the solution is taken from here    b represents the beginning or end of a word  Word Boundary   This regex would match apple in an apple pie  but wouldn   t match apple in pineapple  applecarts or bakeapples  How about    caf       How can we extract the word    caf      in regex  Actually   bcaf   b wouldn   t work  Why  Because    caf      contains non-ASCII character       b can   t be simply used with Unicode such as                   and    When you want to extract Unicode characters  you should directly define characters which represent word boundaries  The answer     lt    s     quot      UNICODE WORD     s     quot        So in order to use the answer in PHP  you can use this function  function contains  str  array  arr           Works in Hebrew and any other unicode characters        Thanks https   medium com  shiba1014 regex-word-boundaries-with-unicode-207794f6e7ed        Thanks https   www phpliveregex com      if  preg match      lt    s     quot            word         s     quot            str   return true     And if you want to search for array of words  you can use this  function arrayContainsWord  str  array  arr        foreach   arr as  word               Works in Hebrew and any other unicode characters            Thanks https   medium com  shiba1014 regex-word-boundaries-with-unicode-207794f6e7ed            Thanks https   www phpliveregex com          if  preg match      lt    s     quot            word         s     quot            str   return true            return false     As of PHP 8 0 0 you can now use str contains  lt  php     if  str contains  abc                  echo  quot Checking the existence of the empty string will always          return true quot

User · Answer

I had some trouble with this  and finally I chose to create my own solution  Without using regular expression engine   function contains  text   word         found   false       spaceArray   explode       text         nonBreakingSpaceArray   explode chr 160    text        if  in array  word   spaceArray             in array  word   nonBreakingSpaceArray                       found   true            return  found       You may notice that the previous solutions are not an answer for the word being used as a prefix for another  In order to use your example    a    How are you     b    a skirt that flares from the waist    c    are     With the samples above  both  a and  b contains  c  but you may want your function to tell you that only  a contains  c

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Another option to finding the occurrence of a word from a string using strstr   and stristr   is like the following    lt  php      a    How are you        if  strstr  a  are        Case sensitive         echo  true       if  stristr  a  are        Case insensitive         echo  true     gt

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You need to use identical not identical operators because strpos can return 0 as it s index value  If you like ternary operators  consider using the following  seems a little backwards I ll admit    echo FALSE     strpos  a  are      false    true

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Use    a    How are you    if  mb strpos  a   are          echo  true       It performs a multi-byte safe strpos   operation

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If you want to avoid the  falsey  and  truthy  problem  you can use substr count   if  substr count  a   are    gt  0        echo  at least one  are  is present        It s a bit slower than strpos but it avoids the comparison problems

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While most of these answers will tell you if a substring appears in your string  that s usually not what you want if you re looking for a particular word  and not a substring   What s the difference   Substrings can appear within other words    The  are  at the beginning of  area  The  are  at the end of  hare  The  are  in the middle of  fares    One way to mitigate this would be to use a regular expression coupled with word boundaries   b    function containsWord  str   word        return   preg match     b    preg quote  word            b i    str       This method doesn t have the same false positives noted above  but it does have some edge cases of its own   Word boundaries match on non-word characters   W   which are going to be anything that isn t a-z  A-Z  0-9  or     That means digits and underscores are going to be counted as word characters and scenarios like this will fail    The  are  in  What  are  you thinking   The  are  in  lol u dunno wut those are4     If you want anything more accurate than this  you ll have to start doing English language syntax parsing  and that s a pretty big can of worms  and assumes proper use of syntax  anyway  which isn t always a given

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Peer to SamGoody and Lego Stormtroopr comments   If you are looking for a PHP algorithm to rank search results based on proximity relevance of multiple words here comes a quick and easy way of generating search results with PHP only   Issues with the other boolean search methods such as strpos    preg match    strstr   or stristr      can t search for multiple words results are unranked    PHP method based on Vector Space Model and tf-idf  term frequency   inverse document frequency    It sounds difficult but is surprisingly easy   If we want to search for multiple words in a string the core problem is how we assign a weight to each one of them   If we could weight the terms in a string based on how representative they are of the string as a whole   we could order our results by the ones that best match the query    This is the idea of the vector space model  not far from how SQL full-text search works   function get corpus index  corpus   array     separator              dictionary   array          doc count   array         foreach  corpus as  doc id   gt   doc              terms   explode  separator   doc             doc count  doc id    count  terms               tf   idf  short for term frequency   inverse document frequency              according to wikipedia is a numerical statistic that is intended to reflect             how important a word is to a document in a corpus          foreach  terms as  term                 if  isset  dictionary  term                        dictionary  term    array  document frequency    gt  0   postings    gt  array                               if  isset  dictionary  term   postings    doc id                        dictionary  term   document frequency                        dictionary  term   postings    doc id    array  term frequency    gt  0                               dictionary  term   postings    doc id   term frequency                           from http   phpir com simple-search-the-vector-space-model              return array  doc count    gt   doc count   dictionary    gt   dictionary      function get similar documents  query      corpus array     separator             similar documents array         if  query     amp  amp  empty  corpus              words explode  separator  query             corpus get corpus index  corpus   separator             doc count count  corpus  doc count              foreach  words as  word                 if isset  corpus  dictionary    word                       entry    corpus  dictionary    word                     foreach  entry  postings   as  doc id   gt   posting                           get term frequency   inverse document frequency                      score  posting  term frequency     log  doc count   1    entry  document frequency     1  2                        if isset  similar documents  doc id                               similar documents  doc id    score                                             else                            similar documents  doc id   score                                                                               length normalise         foreach  similar documents as  doc id   gt   score                  similar documents  doc id     score  corpus  doc count    doc id                          sort from  high to low          arsort  similar documents                  return  similar documents      CASE 1   query    are     corpus   array      1   gt   How are you         match results get similar documents  query  corpus   echo   lt pre gt        print r  match results   echo   lt  pre gt      RESULT  Array        1    gt  0 52832083357372     CASE 2   query    are     corpus   array      1   gt   how are you today        2   gt   how do you do       3   gt   here you are  how are you  Are we done yet        match results get similar documents  query  corpus   echo   lt pre gt        print r  match results   echo   lt  pre gt      RESULTS  Array        1    gt  0 54248125036058      3    gt  0 21699250014423     CASE 3   query    we are done     corpus   array      1   gt   how are you today        2   gt   how do you do       3   gt   here you are  how are you  Are we done yet        match results get similar documents  query  corpus   echo   lt pre gt        print r  match results   echo   lt  pre gt      RESULTS  Array        3    gt  0 6813781191217      1    gt  0 54248125036058     There are plenty of improvements to be made but the model provides a way of getting good results from natural queries   which don t have boolean operators such as strpos    preg match    strstr   or stristr     NOTA BENE  Optionally eliminating redundancy prior to search the words   thereby reducing index size and resulting in less storage requirement less disk I O faster indexing and a consequently faster search    1  Normalisation   Convert all text to lower case    2  Stopword elimination   Eliminate words from the text which carry no real meaning  like  and    or    the    for   etc     3  Dictionary substitution   Replace words with others which have an identical or similar meaning    ex replace instances of  hungrily  and  hungry  with  hunger   Further algorithmic measures  snowball  may be performed to further reduce words to their essential meaning   The replacement of colour names with their hexadecimal equivalents  The reduction of numeric values by reducing precision are other ways of normalising the text    RESOURCES    http   linuxgazette net 164 sephton html http   snowball tartarus org  MySQL Fulltext Search Score Explained http   dev mysql com doc internals en full-text-search html http   en wikipedia org wiki Vector space model http   en wikipedia org wiki Tf E2 80 93idf http   phpir com simple-search-the-vector-space-model

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In order to find a  word   rather than the occurrence of a series of letters that could in fact be a part of another word  the following would be a good solution    string    How are you     array   explode       string    if  in array  are    array          echo  Found the word

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In PHP  the best way to verify if a string contains a certain substring  is to use a simple helper function like this   function contains  haystack   needle   caseSensitive   false        return  caseSensitive                strpos  haystack   needle      FALSE   FALSE   TRUE                stripos  haystack   needle      FALSE   FALSE   TRUE       Explanation    strpos finds the position of the first occurrence of a case-sensitive substring in a string  stripos finds the position of the first occurrence of a case-insensitive substring in a string  myFunction  haystack   needle      FALSE   FALSE   TRUE ensures that myFunction always returns a boolean and fixes unexpected behavior when the index of the substring is 0   caseSensitive   A   B selects either strpos or stripos to do the work  depending on the value of  caseSensitive    Output   var dump contains  bare   are                   Outputs  bool true  var dump contains  stare    are                 Outputs  bool true  var dump contains  stare    Are                 Outputs  bool true  var dump contains  stare    Are   true          Outputs  bool false  var dump contains  hair    are                  Outputs  bool false  var dump contains  aren  t    are               Outputs  bool true  var dump contains  Aren  t    are               Outputs  bool true  var dump contains  Aren  t    are   true        Outputs  bool false  var dump contains  aren  t    Are               Outputs  bool true  var dump contains  aren  t    Are   true        Outputs  bool false  var dump contains  broad    are                 Outputs  bool false  var dump contains  border    are                Outputs  bool false

[php] How do I check if a string contains a specific word?

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