(PHP 4, PHP 5)
substr — Return part of a string
$string
   , int $start
   [, int $length
  ] )
   Returns the portion of string specified by the
   start and length parameters.
  
stringThe input string. Must be one character or longer.
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
       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"
?>
length
       If length is given and is positive, the string
       returned will contain at most length characters
       beginning from start (depending 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 truncation 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"
?>
   Returns the extracted part of string;  or FALSE on failure, or
   an empty string.
  
| Version | Description | 
|---|---|
| 7.0.0 | If stringis equal tostartcharacters long, an empty string will be
        returned. Prior to this version,FALSEwas returned in this case. | 
| 5.2.2 - 5.2.6 | If the startparameter indicates the position of
        a negative truncation or beyond, false is returned. Other versions get
        the string from start. | 
Example #3 Basic substr() 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() 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;
?>
Output of the above example in PHP 7:
1) 'pe' 2) '54' 3) 'gr' 4) '1' 5) '' 6) '' 7) '1200'
Output of the above example in PHP 5:
1) 'pe' 2) '54' 3) 'gr' 4) '1' 5) false 6) false 7) '1200'
   Returns FALSE on error.
   
<?php
var_dump(substr('a', 2)); // bool(false)
?>