strstr() is not a way to avoid type-checking with strpos().
If $needle is the last character in $haystack, and testing $needle as a boolean by itself would evaluate to false, then testing strstr() as a boolean will evaluate to false (because, if successful, strstr() returns the first occurrence of $needle along with the rest of $haystack).
<?php
findZero('01234'); // found a zero
findZero('43210'); // did not find a zero
findZero('0'); // did not find a zero
findZero('00'); // found a zero
findZero('000'); // found a zero
findZero('10'); // did not find a zero
findZero('100'); // found a zero
function findZero($numberString) {
if (strstr($numberString, '0')) {
echo 'found a zero';
} else {
echo 'did not find a zero';
}
}
?>
Also, strstr() is far more memory-intensive than strpos(), especially with longer strings as your $haystack, so if you are not interested in the substring that strstr() returns, you shouldn't be using it anyway.
There is no PHP function just to check only _if_ $needle occurs in $haystack; strpos() tells you if it _doesn't_ by returning false, but, if it does occur, it tells you _where_ it occurs as an integer, which is 0 (zero) if $needle is the first part of $haystack, which is why testing if (strpos($needle, $haystack)===false) is the only way to know for sure if $needle is not part of $haystack.
My advice is to start loving type checking immediately, and to familiarize yourself with the return value of the functions you are using.
Cheers.
strstr
(PHP 4, PHP 5)
strstr — Find the first occurrence of a string
Опис
Returns part of haystack string starting from and including the first
occurrence of needle to the end of
haystack.
Зауваження:
This function is case-sensitive. For case-insensitive searches, use stristr().
Зауваження:
If you only want to determine if a particular
needleoccurs withinhaystack, use the faster and less memory intensive function strpos() instead.
Параметри
-
haystack -
The input string.
-
needle -
If
needleis not a string, it is converted to an integer and applied as the ordinal value of a character. -
before_needle -
If
TRUE, strstr() returns the part of thehaystackbefore the first occurrence of theneedle(excluding the needle).
Значення, що повертаються
Returns the portion of string, or FALSE if needle
is not found.
Журнал Змін
| Версія | Опис |
|---|---|
| 5.3.0 |
Added the optional parameter before_needle.
|
| 4.3.0 | strstr() was made binary safe. |
Приклади
Приклад #1 strstr() example
<?php
$email = 'name@example.com';
$domain = strstr($email, '@');
echo $domain; // prints @example.com
$user = strstr($email, '@', true); // As of PHP 5.3.0
echo $user; // prints name
?>
Прогляньте Також
- stristr() - Case-insensitive strstr
- strrchr() - Find the last occurrence of a character in a string
- strpos() - Знаходить позицію першого входження підрядка в рядку
- strpbrk() - Search a string for any of a set of characters
- preg_match() - Perform a regular expression match
add a note
User Contributed Notes 9 notes
laszlo dot heredy at gmail dot com ¶
10 years ago
gruessle at gmail dot com ¶
13 years ago
Been using this for years:
<?php
/**
*
* @author : Dennis T Kaplan
*
* @version : 1.0
* Date : June 17, 2007
* Function : reverse strstr()
* Purpose : Returns part of haystack string from start to the first occurrence of needle
* $haystack = 'this/that/whatever';
* $result = rstrstr($haystack, '/')
* $result == this
*
* @access public
* @param string $haystack, string $needle
* @return string
**/
function rstrstr($haystack,$needle)
{
return substr($haystack, 0,strpos($haystack, $needle));
}
?>
You could change it to:
rstrstr ( string $haystack , mixed $needle [, int $start] )
<?php
function rstrstr($haystack,$needle, $start=0)
{
return substr($haystack, $start,strpos($haystack, $needle));
}
?>
xslidian at lidian dot info ¶
11 years ago
For those in need of the last occurrence of a string:
<?php
function strrstr($h, $n, $before = false) {
$rpos = strrpos($h, $n);
if($rpos === false) return false;
if($before == false) return substr($h, $rpos);
else return substr($h, 0, $rpos);
}
?>
w3b_monk3y at yahoo dot com ¶
15 years ago
If you want to emulate strstr's new before_needle parameter pre 5.3 strtok is faster than using strpos to find the needle and cutting with substr. The amount of difference varies with string size but strtok is always faster.
brett dot jr dot alton at gmail dot com ¶
16 years ago
For the needle_before (first occurance) parameter when using PHP 5.x or less, try:
<?php
$haystack = 'php-homepage-20071125.png';
$needle = '-';
$result = substr($haystack, 0, strpos($haystack, $needle)); // $result = php
?>
trent dot renshaw at objectst dot com dot au ¶
8 years ago
> root at mantoru dot de
PHP makes this easy for you. When working with domain portion of email addresses, simply pass the return of strstr() to substr() and start at 1:
substr(strstr($haystack, '@'), 1);
root at mantoru dot de ¶
16 years ago
Please note that $needle is included in the return string, as shown in the example above. This ist not always desired behavior, _especially_ in the mentioned example. Use this if you want everything AFTER $needle.
<?php
function strstr_after($haystack, $needle, $case_insensitive = false) {
$strpos = ($case_insensitive) ? 'stripos' : 'strpos';
$pos = $strpos($haystack, $needle);
if (is_int($pos)) {
return substr($haystack, $pos + strlen($needle));
}
// Most likely false or null
return $pos;
}
// Example
$email = 'name@example.com';
$domain = strstr_after($email, '@');
echo $domain; // prints example.com
?>
leo dot nard at free dot fr ¶
18 years ago
When encoding ASCII strings to HTML size-limited strings, sometimes some HTML special chars were cut.
For example, when encoding "��" to a string of size 10, you would get: "à&a" => the second character is cut.
This function will remove any unterminated HTML special characters from the string...
<?php
function cut_html($string)
{
$a=$string;
while ($a = strstr($a, '&'))
{
echo "'".$a."'\n";
$b=strstr($a, ';');
if (!$b)
{
echo "couper...\n";
$nb=strlen($a);
return substr($string, 0, strlen($string)-$nb);
}
$a=substr($a,1,strlen($a)-1);
}
return $string;
}
?>
