php man page for substr

SUBSTR(3)								 1								 SUBSTR(3)

substr - Return part of a string

SYNOPSIS
       string substr (string  $string, int  $start, [int  $length])

DESCRIPTION
	Returns the portion of $string specified by the $start and $length parameters.

PARAMETERS
	      o $string
		- The input string. Must be one character or longer.

	      o $start
		-  If  $start  is  non-negative,  the  returned  string  will  start at the $start'th position in $string, counting from zero. For
		instance, in the string ' abcdef', the character at position 0 is ' a', the character at position 2 is ' c',  and  so  forth.	If
		$start is negative, the returned string will start at the $start'th character from the end of $string.	If $string is less than or
		equal to $start characters long, FALSE will be returned.

	      Example #1

		     Using a negative $start

		     <?php
		     $rest = substr("abcdef", -1);    // returns "f"
		     $rest = substr("abcdef", -2);    // returns "ef"
		     $rest = substr("abcdef", -3, 1); // returns "d"
		     ?>

	      o $length
		- If $length is given and is positive, the string returned will contain at most $length characters beginning from $start  (depend-
		ing  on  the  length  of $string).  If $length is given and is negative, then that many characters will be omitted from the end of
		$string (after the start position has been calculated when a $start is negative). If $start denotes the position of  this  trunca-
		tion  or  beyond,  false  will	be  returned.	If $length is given and is 0, FALSE or NULL, an empty string will be returned.	If
		$length is omitted, the substring starting from $start until the end of the string will be returned.

	      Example #2

		     Using a negative $length

		     <?php
		     $rest = substr("abcdef", 0, -1);  // returns "abcde"
		     $rest = substr("abcdef", 2, -1);  // returns "cde"
		     $rest = substr("abcdef", 4, -4);  // returns false
		     $rest = substr("abcdef", -3, -1); // returns "de"
		     ?>

RETURN VALUES
	Returns the extracted part of $string; or FALSE on failure, or an empty string.

CHANGELOG
       +--------------+---------------------------------------------------+
       |   Version    | 						  |
       |	      | 						  |
       |	      | 		   Description			  |
       |	      | 						  |
       +--------------+---------------------------------------------------+
       |5.2.2 - 5.2.6 | 						  |
       |	      | 						  |
       |	      |  If the $start parameter indicates  the  position |
       |	      | of  a  negative  truncation  or  beyond, false is |
       |	      | returned. Other  versions  get	the  string  from |
       |	      | start.						  |
       |	      | 						  |
       +--------------+---------------------------------------------------+
EXAMPLES
       Example #3

	      Basic substr(3) usage

	      <?php
	      echo substr('abcdef', 1);     // bcdef
	      echo substr('abcdef', 1, 3);  // bcd
	      echo substr('abcdef', 0, 4);  // abcd
	      echo substr('abcdef', 0, 8);  // abcdef
	      echo substr('abcdef', -1, 1); // f

	      // Accessing single characters in a string
	      // can also be achieved using "square brackets"
	      $string = 'abcdef';
	      echo $string[0];		       // a
	      echo $string[3];		       // d
	      echo $string[strlen($string)-1]; // f

	      ?>

       Example #4

	      substr(3) casting behaviour

	      <?php
	      class apple {
		  public function __toString() {
		      return "green";
		  }
	      }

	      echo "1) ".var_export(substr("pear", 0, 2), true).PHP_EOL;
	      echo "2) ".var_export(substr(54321, 0, 2), true).PHP_EOL;
	      echo "3) ".var_export(substr(new apple(), 0, 2), true).PHP_EOL;
	      echo "4) ".var_export(substr(true, 0, 1), true).PHP_EOL;
	      echo "5) ".var_export(substr(false, 0, 1), true).PHP_EOL;
	      echo "6) ".var_export(substr("", 0, 1), true).PHP_EOL;
	      echo "7) ".var_export(substr(1.2e3, 0, 4), true).PHP_EOL;
	      ?>

	      The above example will output:

	      1) 'pe'
	      2) '54'
	      3) 'gr'
	      4) '1'
	      5) false
	      6) false
	      7) '1200'

ERRORS
/EXCEPTIONS
	Returns FALSE on error.

       Example #5

	      <?php
	      var_dump(substr('a', 1)); // bool(false)
	      ?>

SEE ALSO
       strrchr(3), substr_replace(3), preg_match(3), trim(3), mb_substr(3), wordwrap(3), String access and modification by character.

PHP Documentation Group 														 SUBSTR(3)