The Microwave team has now decided to start writing down all of the small tricks and tips that they find whilst developing…
This is the basic theory behind what we are going to do and what lots of people start looking at to achieve their goal…
Description
string substr ( string $string , int $start [, int $length ] )Returns the portion of string specified by the start and length parameters.
Parameters
- string
-
The input string.
- 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"
?> - 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 astart is negative). If start denotes a position beyond this truncation, an empty string will be returned.
If length is given and is 0, FALSE or NULL an empty 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 ""
$rest = substr("abcdef", -3, -1); // returns "de"
?>
Return Values
Returns the extracted part of string or FALSE on failure.
Examples
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
?>
Errors/Exceptions
Returns FALSE on error.
<?php
var_dump(substr('a', 1)); // bool(false)
?>
Information source: http://php.net/manual/en/function.substr.php
