我如何编写两个函数,如果它以指定的字符/字符串开头或以指定的字符串结尾,那么它们将接受字符串并返回?
例如:
$str = '|apples}';
echo startsWith($str, '|'); //Returns true
echo endsWith($str, '}'); //Returns true
我如何编写两个函数,如果它以指定的字符/字符串开头或以指定的字符串结尾,那么它们将接受字符串并返回?
例如:
$str = '|apples}';
echo startsWith($str, '|'); //Returns true
echo endsWith($str, '}'); //Returns true
当前回答
简而言之:
function startsWith($str, $needle){
return substr($str, 0, strlen($needle)) === $needle;
}
function endsWith($str, $needle){
$length = strlen($needle);
return !$length || substr($str, - $length) === $needle;
}
其他回答
function startsWith($haystack, $needle, $case = true) {
if ($case) {
return (strcmp(substr($haystack, 0, strlen($needle)), $needle) === 0);
}
return (strcasecmp(substr($haystack, 0, strlen($needle)), $needle) === 0);
}
function endsWith($haystack, $needle, $case = true) {
if ($case) {
return (strcmp(substr($haystack, strlen($haystack) - strlen($needle)), $needle) === 0);
}
return (strcasecmp(substr($haystack, strlen($haystack) - strlen($needle)), $needle) === 0);
}
贷方:
检查字符串是否以另一个字符串结尾
检查字符串是否以另一个字符串开头
PHP 8.0及更高版本
从PHP 8.0开始,您可以使用
str_starts_with手册和
str_ends_with手动
实例
echo str_starts_with($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 ) === $needle;
}
到目前为止,所有的答案似乎都做了大量不必要的工作、strlen计算、字符串分配(substr)等。“strpos”和“stripos”函数返回$haystack中$needle第一次出现的索引:
function startsWith($haystack,$needle,$case=true)
{
if ($case)
return strpos($haystack, $needle, 0) === 0;
return stripos($haystack, $needle, 0) === 0;
}
function endsWith($haystack,$needle,$case=true)
{
$expectedPosition = strlen($haystack) - strlen($needle);
if ($case)
return strrpos($haystack, $needle, 0) === $expectedPosition;
return strripos($haystack, $needle, 0) === $expectedPosition;
}
这是一个接受答案的多字节安全版本,它适用于UTF-8字符串:
function startsWith($haystack, $needle)
{
$length = mb_strlen($needle, 'UTF-8');
return (mb_substr($haystack, 0, $length, 'UTF-8') === $needle);
}
function endsWith($haystack, $needle)
{
$length = mb_strlen($needle, 'UTF-8');
return $length === 0 ||
(mb_substr($haystack, -$length, $length, 'UTF-8') === $needle);
}
上面的正则表达式函数,但上面还建议了其他调整:
function startsWith($needle, $haystack) {
return preg_match('/^' . preg_quote($needle, '/') . '/', $haystack);
}
function endsWith($needle, $haystack) {
return preg_match('/' . preg_quote($needle, '/') . '$/', $haystack);
}