strstr

(PHP 4, PHP 5, PHP 7, PHP 8)

strstr — Find the first occurrence of a string

Опис

strstr(string $haystack, string $needle, bool $before_needle = false): string|false

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 it is only required to determine if a particular needle occurs within haystack, the faster and less memory intensive str_contains() function should be used instead.

Параметри

haystack

The input string.

needle

The string to search for.

До версії PHP 8.0.0, якщо параметр needle не є рядком, він перетворюється на ціле число і розглядається як код символу. Ця поведінка є застарілою, починаючи з PHP 7.3.0. Вкрай не рекомендується на неї покладатися. Залежно від потрібної поведінки, параметр needle необхідно привести до рядкового типу або обробити функцією chr().

before_needle

If true, strstr() returns the part of the haystack before the first occurrence of the needle (excluding the needle).

Значення, що повертаються

Returns the portion of string, or false if needle is not found.

Журнал змін

Версія	Опис
8.0.0	Тепер параметр `needle` може бути порожнім рядком.
8.0.0	Passing an int as `needle` is no longer supported.
7.3.0	Passing an int as `needle` has been deprecated.

Приклади

Приклад #1 strstr() example

<?php
$email  = 'name@example.com';
$domain = strstr($email, '@');
echo $domain; // prints @example.com

$user = strstr($email, '@', true);
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

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User Contributed Notes 8 notes

down

laszlo dot heredy at gmail dot com ¶

11 years ago

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.

down

Julian Egelstaff ¶

1 year ago

Lookout for logic inversion in old code!



In PHP 8, if the needle is an empty string, this function will return 0 (not false), implying the first character of the string matches the needle. Before PHP 8, it would return false when the needle is an empty string.



There other string functions that are affected by similar issues in PHP 8: strpos(), strrpos(), stripos(), strripos(), strchr(), strrchr(), stristr(), and this function, strstr()



If you are checking if the return value === false then you will be misled by this new behaviour. You also need to check if the needle was an empty string. Basically, something like this:



<?php

$result = $needle ? strstr($haystack, $needle) : false;

?>

down

Gevorg Melkumyan ¶

3 years ago

Don't confuse this function with strtr ) I lost like 1 hour on that

down

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);
}
?>

down

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));
    }

?>

down

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.

down

brett dot jr dot alton at gmail dot com ¶

17 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
?>

down

-3

trent dot renshaw at objectst dot com dot au ¶

9 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);

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