PHP 8.0及更高版本

从PHP 8.0开始，您可以使用

str_starts_with手册和

str_ends_with手动

实例

echo str_starts_with（$str，'|'）；

8.0之前的PHP

function startsWith( $haystack, $needle ) {
     $length = strlen( $needle );
     return substr( $haystack, 0, $length ) === $needle;
}

function endsWith( $haystack, $needle ) {
    $length = strlen( $needle );
    if( !$length ) {
        return true;
    }
    return substr( $haystack, -$length ) === $needle;
}

为什么不采取以下措施？

//How to check if a string begins with another string
$haystack = "valuehaystack";
$needle = "value";
if (strpos($haystack, $needle) === 0){
    echo "Found " . $needle . " at the beginning of " . $haystack . "!";
}

输出：

在valuehaystack的开头找到值！

请记住，如果在干草堆中没有找到针，strpos将返回false，如果且仅当在索引0处找到针时（即开头），strpos将返回0。

以下是结尾：

$haystack = "valuehaystack";
$needle = "haystack";

//If index of the needle plus the length of the needle is the same length as the entire haystack.
if (strpos($haystack, $needle) + strlen($needle) === strlen($haystack)){
    echo "Found " . $needle . " at the end of " . $haystack . "!";
}

在这种情况下，不需要函数startsWith（）作为

(strpos($stringToSearch, $doesItStartWithThis) === 0)

将准确返回true或false。

奇怪的是，这么简单，所有的野生函数都在这里泛滥。

您可以使用strpos和strrpos

$bStartsWith = strpos($sHaystack, $sNeedle) == 0;
$bEndsWith = strrpos($sHaystack, $sNeedle) == strlen($sHaystack)-strlen($sNeedle);

mpen给出的答案非常彻底，但不幸的是，提供的基准有一个非常重要且有害的监督。

因为针和草堆中的每个字节都是完全随机的，所以针-草堆对在第一个字节上不同的概率为99.609375%，这意味着平均而言，100000对中的大约99609对在第一字节上不同。换言之，基准测试严重偏向于显式检查第一个字节的startswith实现，正如strncmp_startswith2所做的那样。

如果测试生成循环按如下方式实现：

echo 'generating tests';
for($i = 0; $i < 100000; ++$i) {
    if($i % 2500 === 0) echo '.';

    $haystack_length = random_int(1, 7000);
    $haystack = random_bytes($haystack_length);

    $needle_length = random_int(1, 3000);
    $overlap_length = min(random_int(0, $needle_length), $haystack_length);
    $needle = ($needle_length > $overlap_length) ?
        substr($haystack, 0, $overlap_length) . random_bytes($needle_length - $overlap_length) :
        substr($haystack, 0, $needle_length);

    $test_cases[] = [$haystack, $needle];
}
echo " done!<br />";

基准测试结果讲述了一个略有不同的故事：

strncmp_startswith: 223.0 ms
substr_startswith: 228.0 ms
substr_compare_startswith: 238.0 ms
strncmp_startswith2: 253.0 ms
strpos_startswith: 349.0 ms
preg_match_startswith: 20,828.7 ms

当然，这个基准可能仍然不是完全无偏的，但它也测试了当给定部分匹配的针时算法的效率。

根据詹姆斯·布莱克的回答，以下是其结尾版本：

function startsWith($haystack, $needle, $case=true) {
    if ($case)
        return strncmp($haystack, $needle, strlen($needle)) == 0;
    else
        return strncasecmp($haystack, $needle, strlen($needle)) == 0;
}

function endsWith($haystack, $needle, $case=true) {
     return startsWith(strrev($haystack),strrev($needle),$case);

}

注意：我已将if else部分替换为James Black的startsWith函数，因为strncasecmp实际上是strncmp的不区分大小写版本。

Fastest endsWith（）解决方案：

# Checks if a string ends in a string
function endsWith($haystack, $needle) {
    return substr($haystack,-strlen($needle))===$needle;
}

基准：

# This answer
function endsWith($haystack, $needle) {
    return substr($haystack,-strlen($needle))===$needle;
}

# Accepted answer
function endsWith2($haystack, $needle) {
    $length = strlen($needle);

    return $length === 0 ||
    (substr($haystack, -$length) === $needle);
}

# Second most-voted answer
function endsWith3($haystack, $needle) {
    // search forward starting from end minus needle length characters
    if ($needle === '') {
        return true;
    }
    $diff = \strlen($haystack) - \strlen($needle);
    return $diff >= 0 && strpos($haystack, $needle, $diff) !== false;
}

# Regex answer
function endsWith4($haystack, $needle) {
    return preg_match('/' . preg_quote($needle, '/') . '$/', $haystack);
}

function timedebug() {
    $test = 10000000;

    $time1 = microtime(true);
    for ($i=0; $i < $test; $i++) {
        $tmp = endsWith('TestShortcode', 'Shortcode');
    }
    $time2 = microtime(true);
    $result1 = $time2 - $time1;

    for ($i=0; $i < $test; $i++) {
        $tmp = endsWith2('TestShortcode', 'Shortcode');
    }
    $time3 = microtime(true);
    $result2 = $time3 - $time2;

    for ($i=0; $i < $test; $i++) {
        $tmp = endsWith3('TestShortcode', 'Shortcode');
    }
    $time4 = microtime(true);
    $result3 = $time4 - $time3;

    for ($i=0; $i < $test; $i++) {
        $tmp = endsWith4('TestShortcode', 'Shortcode');
    }
    $time5 = microtime(true);
    $result4 = $time5 - $time4;

    echo $test.'x endsWith: '.$result1.' seconds # This answer<br>';
    echo $test.'x endsWith2: '.$result4.' seconds # Accepted answer<br>';
    echo $test.'x endsWith3: '.$result2.' seconds # Second most voted answer<br>';
    echo $test.'x endsWith4: '.$result3.' seconds # Regex answer<br>';
    exit;
}
timedebug();

基准结果：

10000000x endsWith: 1.5760900974274 seconds # This answer
10000000x endsWith2: 3.7102129459381 seconds # Accepted answer
10000000x endsWith3: 1.8731069564819 seconds # Second most voted answer
10000000x endsWith4: 2.1521229743958 seconds # Regex answer