PHP preg match - only allow alphanumeric strings and - characters

Question

I need the regex to check if a string only contains numbers  letters  hyphens or underscore   string1    This is a string     string2    this is-a-string    if preg match            string1      echo  String 1 not acceptable acceptable         String2 acceptable

User · Accepted Answer

Code   if preg match     a-z  -0-9  i    string       echo  not valid string       Explanation          character class definition      negate the class a-z    chars from  a  to  z       underscore -    hyphen  -   You need to escape it  0-9    numbers  from zero to nine    The  i  modifier at the end of the regex is for  case-insensitive  if you don t put that you will need to add the upper case characters in the code before by doing A-Z

User · Answer

if  preg match      w-        string1        echo  String 1 not acceptable acceptable         String2 acceptable

User · Answer

Here is one equivalent of the accepted answer for the UTF-8 world   if   preg match      p L  p N  -    u    string        Disallowed Character In  string     Explanation          character class definition p L     matches any kind of letter character from any language p N     matches any kind of numeric character  -    matches underscore and hyphen      Quantifier     Matches between one to unlimited times  greedy    u    Unicode modifier  Pattern strings are treated as UTF-16  Also causes escape sequences to match unicode characters   Note  that if the hyphen is the last character in the class definition it does not need to be escaped  If the dash appears elsewhere in the class definition it needs to be escaped  as it will be seen as a range character rather then a hyphen

User · Answer

Why to use regex  PHP has some built in functionality to do that   lt  php      valid symbols   array  -              string1    This is a string         string2    this is-a-string        if preg match    s    string1      ctype alnum str replace  valid symbols       string1              echo  String 1 not acceptable acceptable           gt    preg match    s    username  will check for blank space   ctype alnum str replace  valid symbols       string1   will check for valid symbols

User · Answer

w - is probably the best but here just another alternative Use   alnum    if  preg match       alnum   -      str   echo  valid     demo1   demo2

[php] PHP preg_match - only allow alphanumeric strings and - _ characters

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