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, PHP 7, PHP 8)
strstr — Encontra a primeira ocorrencia de uma string
Descrição
Retorna parte da string haystack a partir da primeira
ocorrência de needle até o final de
haystack.
Nota:
Esta função diferencia maiúsculas e minúsculas. Para pesquisas que não diferenciem, use stristr().
Nota:
Se você quer somente determinar se um específica
needleexistem emhaystack, use a função mais rápida e que usa menos memória ao invés, strpos().
Parâmetros
-
haystack -
A string de entrada.
-
needle -
Se
needlenão é uma string, é convertido para um inteiro e aplicado como valor ordinal de um caractere. -
before_needle -
Se
true(o padrão éfalse), strstr() retorna a parte dehaystackantes da primeira ocorrência deneedle.
Valor Retornado
Retorna a parte da string, ou false se needle
não é encontrado.
Changelog
| Versão | Descrição |
|---|---|
| 5.3.0 |
Adicionado o parâmetro opcional before_needle.
|
| 4.3.0 | strstr() tornou-se binary safe. |
Exemplos
Exemplo #1 Exemplo da strstr()
<?php
$email = 'name@example.com';
$domain = strstr($email, '@');
echo $domain; // prints @example.com
$user = strstr($email, '@', true); // A partir do PHP 5.3.0
echo $user; // prints name
?>
Veja Também
- preg_match() - Perform a regular expression match
- stristr() - strstr sem diferenciar maiúsculas e minúsculas
- strpos() - Encontra a posição da primeira ocorrência de uma string
- strrchr() - Encontra a ultima ocorrência de um caractere em uma string
- substr() - Retorna uma parte de uma string
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;
}
?>
