Regular expressions

Regular expressions are used for complex string manipulation in PHP. The functions that support regular expressions are:

These functions all take a regular expression string as their first argument. PHP uses the POSIX extended regular expressions as defined by POSIX 1003.2. For a full description of POSIX regular expressions see the regex man pages included in the regex directory in the PHP distribution.

Example 4-5. Regular expression examples

ereg("abc",$string);            
/* Returns true if "abc"
   is found anywhere in $string. */

ereg("^abc",$string);
/* Returns true if "abc"
   is found at the beginning of $string. */

ereg("abc$",$string);
/* Returns true if "abc"
   is found at the end of $string. */

eregi("(ozilla.[23]|MSIE.3)",$HTTP_USER_AGENT);  
/* Returns true if client browser
   is Netscape 2, 3 or MSIE 3. */

ereg("([[:alnum:]]+) ([[:alnum:]]+) ([[:alnum:]]+)",
     $string,$regs); 
/* Places three space separated words
   into $regs[1], $regs[2] and $regs[3]. */

ereg_replace("^","<BR>",$string); 
/* Put a <BR> tag at the beginning of $string. */
 
ereg_replace("$","<BR>",$string); 
/* Put a <BR> tag at the end of $string. */

ereg_replace("\n","",$string);
/* Get rid of any carriage return
   characters in $string. */