Using str replace so that it only acts on the first match

Question

I want a version of str replace   that only replaces the first occurrence of  search in the  subject  Is there an easy solution to this  or do I need a hacky solution

User · Answer

string    this is my world  not my world    find    world    replace    farm    result   preg replace    find    replace  string 1   echo  result

User · Answer

If you string does not contains any multibyte characters and if you want to replace only one char you can simply use strpos  Here a function who handle errors         Replace the first occurence of given string        param  string  search  a char to search in   subject      param  string  replace a char to replace in   subject      param  string  subject     return string        throws InvalidArgumentException if   search  or   replace  are invalid or if   subject  is a multibytes string     function str replace first string  search   string  replace   string  subject    string          check params     if strlen  replace     1    strlen  search     1            throw new InvalidArgumentException   search  amp   replace must be char         elseif mb strlen  subject     strlen  subject            throw new InvalidArgumentException   subject is an multibytes string                 search       pos   strpos  subject   search       if  pos     false               not found         return  subject                replace      subject  replace     subject       return  subject

User · Answer

Unfortunately  I don t know of any PHP function which can do this  You can roll your own fairly easily like this   function replace first  find   replace   subject           stolen from the comments at PHP net str replace        Splits  subject into an array of 2 items by  find         and then joins the array with  replace     return implode  replace  explode  find   subject  2

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str    Hello there folks    str ex   explode  there   str  2       explodes  string just twice                                         outputs  array   Hello      folks    str final   implode      str ex         glues above array together                                          outputs  str  Hello  folks     There is one more additional space but it didnt matter as it was for backgound script in my case

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This function is heavily inspired by the answer by  renocor  It makes the function multi byte safe   function str replace limit  search   replace   string   limit         i   0       searchLength   mb strlen  search        while   pos   mb strpos  string   search       false  amp  amp   i  lt   limit                 string   mb substr replace  string   replace   pos   searchLength            i    1             return  string     function mb substr replace  string   replacement   start   length   null   encoding   null         string    array  string       encoding   is null  encoding    mb internal encoding      encoding       length   is null  length    mb strlen  string  -  start    length        string   array map function  str  use   replacement   start   length   encoding             begin   mb substr  str  0   start   encoding            end   mb substr  str    start    length   mb strlen  str    encoding            return  begin    replacement    end           string        return   count  string      1      string 0     string

User · Answer

There s no version of it  but the solution isn t hacky at all    pos   strpos  haystack   needle   if   pos     false         newstring   substr replace  haystack   replace   pos  strlen  needle        Pretty easy  and saves the performance penalty of regular expressions   Bonus  If you want to replace last occurrence  just use strrpos in place of strpos

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I wondered which one was the fastest  so I tested them all   Below you will find    A comprehensive list of all the functions that have been contributed onto this page Benchmark testing for each contrubution  average execution time over 10 000 runs  Links to each answer  for the full code      All functions were tested with the same settings    string    OOO OOO OOO S    search    OOO     replace    B       Functions that only replace the first occurrence of a string within a string    substr replace  string   replace  0  strlen  search      CONTRIBUTED BY    gt  zombat  OOO OOO OOO S    gt  B OOO OOO S  AVERAGE TIME    gt  0 0000062883  SLOWER BY    gt  FASTEST  replace first  search   replace   string     CONTRIBUTED BY    gt  too much php  OOO OOO OOO S    gt  B OOO OOO S  AVERAGE TIME    gt  0 0000073902  SLOWER BY    gt  17 52   preg replace  search   replace   string  1     CONTRIBUTED BY    gt  karim79  OOO OOO OOO S    gt  B OOO OOO S  AVERAGE TIME    gt  0 0000077519  SLOWER BY    gt  23 27   str replace once  search   replace   string     CONTRIBUTED BY    gt  happyhardik  OOO OOO OOO S    gt  B OOO OOO S  AVERAGE TIME    gt  0 0000082286  SLOWER BY    gt  30 86   str replace limit  search   replace   string   count  1     CONTRIBUTED BY    gt  bfrohs - expanded renocor  OOO OOO OOO S    gt  B OOO OOO S  AVERAGE TIME    gt  0 0000083342  SLOWER BY    gt  32 54   str replace limit  search   replace   string  1     CONTRIBUTED BY    gt  renocor  OOO OOO OOO S    gt  B OOO OOO S  AVERAGE TIME    gt  0 0000093116  SLOWER BY    gt  48 08   str replace limit  string   search   replace  1  0     CONTRIBUTED BY    gt  jayoaK  OOO OOO OOO S    gt  B OOO OOO S  AVERAGE TIME    gt  0 0000093862  SLOWER BY    gt  49 26       Functions that only replace the last occurrence of a string within a string    substr replace  string   replace  strrpos  string   search   strlen  search      CONTRIBUTED BY    gt  oLinkSoftware - modified zombat  OOO OOO OOO S    gt  OOO OOO B S  AVERAGE TIME    gt  0 0000068083  SLOWER BY    gt  FASTEST  strrev implode strrev  replace   explode strrev  search   strrev  string   2       CONTRIBUTED BY    gt  oLinkSoftware  OOO OOO OOO S    gt  OOO OOO B S  AVERAGE TIME    gt  0 0000084460  SLOWER BY    gt  24 05

User · Answer

For Loop Solution   lt  php echo replaceFirstMatchedChar   amp           property details amp id 202 amp test 123 tab-6     function replaceFirstMatchedChar  searchChar   replaceChar   str        for   i   0   i  lt  strlen  str    i               if   str  i      searchChar                 str  i     replaceChar              break                      return  str

User · Answer

The easiest way would be to use regular expression   The other way is to find the position of the string with strpos   and then an substr replace    But i would really go for the RegExp

User · Answer

According to my test result  I d like to vote the regular express one provided by karim79   I don t have enough reputation to vote it now    The solution from zombat uses too many function calls  I even simplify the codes  I m using PHP 5 4 to run both solutions for 100 000 times  and here s the result    str    Hello abc  have a nice day abc  abc     pos   strpos  str   abc     str   substr replace  str   123    pos  3         1 85 sec   str    Hello abc  have a nice day abc  abc     str   preg replace   abc     123    str  1         1 35 sec  As you can see  The performance of preg replace is not so bad as many people think  So I d suggest the classy solution if your regular express is not complicated

User · Answer

For a string   string    OOO OOO OOO S    search    OOO    replace    B      replace ONLY FIRST occurance of  OOO  with  B       string   substr replace  string  replace 0 strlen  search           string   gt  B OOO OOO S    replace ONLY LAST occurance of  OOOO  with  B       string   substr replace  string  replace strrpos  string  search  strlen  search           string   gt  OOO OOO B S        replace ONLY LAST occurance of  OOOO  with  B       string   strrev implode strrev  replace  explode strrev  search  strrev  string  2           string   gt  OOO OOO B S   For a single character   string strpos  string  search      replace      EXAMPLE   string    O O O O S    search    O    replace    B      replace ONLY FIRST occurance of  O  with  B        string strpos  string  search      replace           string   gt  B O O O S    replace ONLY LAST occurance of  O  with  B        string strrpos  string  search      replace           string   gt  B O O B S

User · Answer

str     property details amp id 202 amp test 123 tab-6p    position   strpos  str   amp     echo substr replace  str      position 1     Using substr replace we can replace the occurrence of first character only in string  as  amp  is repeated multiple times but only at first position we have to replace  amp  with

User · Answer

Can be done with preg replace   function str replace first  from   to   content         from       preg quote  from                 return preg replace  from   to   content  1      echo str replace first  abc    123    abcdef abcdef abcdef        outputs  123def abcdef abcdef    The magic is in the optional fourth parameter  Limit   From the documentation       Limit  - The maximum possible   replacements for each pattern in each   subject string  Defaults to -1  no   limit     Though  see zombat s answer for a more efficient method  roughly  3-4x faster

User · Answer

CODE WAS REVISED  so consider some comments too old     And thanks everyone on helping me to improve that      Any BUG  please communicate me  I ll fix that up right after   So  lets go for   Replacing the first  o  to  ea  for example    s  I love you    s str replace first  o   ea   s   echo  s     output  I leave you   The function   function str replace first  a  b  s                       w strpos  s  a            if  w   false return  s           return substr  s 0  w   b substr  s  w strlen  a

User · Answer

Complementing what people said  remember that the entire string is an array    string    Lorem ipsum l   l   l       string 0     B    echo  string     Borem ipsum l   l   l

User · Answer

To expand on  renocor s answer  I ve written a function that is 100  backward-compatible with str replace    That is  you can replace all occurrences of str replace   with str replace limit   without messing anything up  even those using arrays for the  search   replace  and or  subject   The function could be completely self-contained  if you wanted to replace the function call with   string   strval intval strval  string      but I d recommend against it since valid integer   is a rather useful function when dealing with integers provided as strings   Note  Whenever possible  str replace limit   will use str replace   instead  so all calls to str replace   can be replaced with str replace limit   without worrying about a hit to performance   Usage   lt  php  search    a    replace    b    subject    abcabc        limit   -1     No limit  new string   str replace limit  search   replace   subject   count   limit   echo  count   replacements --    new string       2 replacements -- bbcbbc    limit   1     Limit of 1  new string   str replace limit  search   replace   subject   count   limit   echo  count   replacements --    new string       1 replacements -- bbcabc    limit   10     Limit of 10  new string   str replace limit  search   replace   subject   count   limit   echo  count   replacements --    new string       2 replacements -- bbcbbc   Function   lt  php         Checks if  string is a valid integer  Integers provided as strings  e g   2  vs 2     are also supported      param mixed  string     return bool Returns boolean TRUE if string is a valid integer  or FALSE if it is not      function valid integer  string          1  Cast as string  in case integer is provided         1  Convert the string to an integer and back to a string        2  Check if identical  note   identical   NOT just  equal          Note  TRUE  FALSE  and NULL  string values all return FALSE      string   strval  string       return   string   strval intval  string               Replace  limit occurences of the search string with the replacement string     param mixed  search The value being searched for  otherwise known as the needle  An    array may be used to designate multiple needles      param mixed  replace The replacement value that replaces found search values  An    array may be used to designate multiple replacements      param mixed  subject The string or array being searched and replaced on  otherwise    known as the haystack  If subject is an array  then the search and replace is    performed with every entry of subject  and the return value is an array as well       param string  count If passed  this will be set to the number of replacements    performed      param int  limit The maximum possible replacements for each pattern in each subject    string  Defaults to -1  no limit       return string This function returns a string with the replaced values      function str replace limit           search           replace           subject           amp  count           limit   -1                Set some defaults      count   0          Invalid  limit provided  Throw a warning      if  valid integer  limit             backtrace   debug backtrace            trigger error  Invalid  limit     limit    provided to     function       in                         backtrace 0   file      on line    backtrace 0   line      Expecting an                     integer   E USER WARNING           return  subject                Invalid  limit provided  Throw a warning      if  limit lt -1            backtrace   debug backtrace            trigger error  Invalid  limit     limit    provided to     function       in                         backtrace 0   file      on line    backtrace 0   line      Expecting -1 or                     a positive integer   E USER WARNING           return  subject                No replacements necessary  Throw a notice as this was most likely not the intended        use  And  if it was  e g  part of a loop  setting  limit dynamically   it can be        worked around by simply checking to see if  limit   0  and if it does  skip the        function call  and set  count to 0  if applicable       if  limit   0            backtrace   debug backtrace            trigger error  Invalid  limit     limit    provided to     function       in                         backtrace 0   file      on line    backtrace 0   line      Expecting -1 or                     a positive integer   E USER NOTICE           return  subject                Use str replace   whenever possible  for performance reasons      if  limit   -1           return str replace  search   replace   subject   count              if is array  subject                Loop through  subject values and call this function for each one          foreach  subject as  key   gt   this subject                   Skip values that are arrays  to match str replace                 if  is array  this subject                        Call this function again for                  this function     FUNCTION                     subject  key     this function                           search                           replace                           this subject                           this count                           limit                                        Adjust  count                  count     this count                      Adjust  limit  if not -1                 if  limit  -1                        limit -   this count                                        Reached  limit  return  subject                 if  limit   0                       return  subject                                                       return  subject         elseif is array  search               Only treat  replace as an array if  search is also an array  to match str replace                Clear keys of  search  to match str replace              search   array values  search               Clear keys of  replace  if applicable  to match str replace             if is array  replace                 replace   array values  replace                         Loop through  search array          foreach  search as  key   gt   this search                   Don t support multi-dimensional arrays  to match str replace                  this search   strval  this search                   If  replace is an array  use the value of  replace  key  as the replacement  If                 replace  key  doesn t exist  just an empty string  to match str replace                 if is array  replace                    if array key exists  key   replace                         this replace   strval  replace  key                      else                        this replace                                       else                    this replace   strval  replace                                 Call this function again for              this function     FUNCTION                 subject    this function                       this search                       this replace                       subject                       this count                       limit                                Adjust  count              count     this count                  Adjust  limit  if not -1             if  limit  -1                    limit -   this count                                Reached  limit  return  subject             if  limit   0                   return  subject                                    return  subject         else            search   strval  search            replace   strval  replace               Get position of first  search          pos   strpos  subject   search               Return  subject if  search cannot be found         if  pos   false               return  subject                        Get length of  search  to make proper replacement later on          search len   strlen  search               Loop until  search can no longer be found  or  limit is reached         for  i 0    i lt  limit     limit   -1    i                     Replace               subject   substr replace  subject   replace   pos   search len                   Increase  count              count                    Get location of next  search              pos   strpos  subject   search                   Break out of loop if  needle             if  pos   false                   break                                       Return new  subject         return  subject

User · Answer

I created this little function that replaces string on string  case-sensitive  with limit  without the need of Regexp  It works fine   function str replace limit  search   replace   string   limit   1         pos   strpos  string   search        if   pos     false            return  string              searchLen   strlen  search        for   i   0   i  lt   limit   i               string   substr replace  string   replace   pos   searchLen             pos   strpos  string   search            if   pos     false                break                       return  string      Example usage    search     foo    replace    bar    string     foo wizard makes foo brew for evil foo and jack    limit     2    replaced   str replace limit  search   replace   string   limit    echo  replaced     bar wizard makes bar brew for evil foo and jack

User · Answer

To expand on zombat s answer  which I believe to be the best answer   I created a recursive version of his function that takes in a  limit parameter to specify how many occurrences you want to replace   function str replace limit  haystack   needle   replace   limit   start pos   0        if   limit  lt   0            return  haystack        else            pos   strpos  haystack  needle  start pos           if   pos     false                 newstring   substr replace  haystack   replace   pos  strlen  needle                return str replace limit  newstring   needle   replace   limit-1   pos strlen  replace              else               return  haystack

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Edit  both answers have been updated and are now correct  I ll leave the answer since the function timings are still useful   The answers by  zombat  and  too much php  are unfortunately not correct  This is a revision to the answer zombat posted  as I don t have enough reputation to post a comment     pos   strpos  haystack  needle   if   pos     false         newstring   substr replace  haystack  replace  pos strlen  needle        Note the strlen  needle   instead of strlen  replace   Zombat s example will only work correctly if needle and replace are the same length    Here s the same functionality in a function with the same signature as PHP s own str replace   function str replace first  search   replace   subject         pos   strpos  subject   search       if   pos     false            return substr replace  subject   replace   pos  strlen  search              return  subject      This is the revised answer of  too much php    implode  replace  explode  search   subject  2      Note the 2 at the end instead of 1  Or in function format   function str replace first  search   replace   subject        return implode  replace  explode  search   subject  2        I timed the two functions and the first one is twice as fast when no match is found  They are the same speed when a match is found

User · Answer

You can use this   function str replace once  str pattern   str replacement   string             if  strpos  string   str pattern      false                 occurrence   strpos  string   str pattern                return substr replace  string   str replacement  strpos  string   str pattern   strlen  str pattern                         return  string            Found this example from php net  Usage    string    Thiz iz an examplz   var dump str replace once  z   Z    string       Output   ThiZ iz an examplz   This may reduce the performance a little bit  but the easiest solution

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function str replace once  search   replace   subject         pos   strpos  subject   search       if   pos     false            return  subject             return substr  subject  0   pos     replace   substr  subject   pos   strlen  search

User · Answer

Here s a simple class I created to wrap our slightly modified str replace   functions   Our php  str rreplace   function also allows you to carry out a reverse  limited str replace   which can be very handy when trying to replace only the final X instance s  of a string   These examples both use preg replace      lt  php class php                  str replace   from the end of a string that can also be limited e g  replace only the last instance of   lt  div gt   with                 param string    find        param string    replace        param string    subject        param int       replacement limit   -1 to replace all references              return string            public static function str replace  find   replace   subject   replacement limit   -1             find pattern   str replace             find           return preg replace        find pattern         replace   subject   replacement limit                        str replace   from the end of a string that can also be limited e g  replace only the last instance of   lt  div gt   with                 param string    find        param string    replace        param string    subject        param int       replacement limit   -1 to replace all references              return string            public static function str rreplace  find   replace   subject   replacement limit   -1            return strrev  self  str replace strrev  find   strrev  replace   strrev  subject    replacement limit

[php] Using str_replace so that it only acts on the first match?

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