PHP 判断是否包含在某个字符串中

1.用strpos函数，查找字符首次出现的位置，如果不存在则会返回false
$str= 'abc';
$needle= 'e';
$pos = strpos($str, $needle);
2.用strstr函数查找字符在字符串中首次出现，并返回字符出现开始的位置至结束的字符串
$email = 'user@example.com';
$domain = strstr($email, '@');
3.用explode分割字符串，如果返回的数组长度大于一则表示存在
$str= 'abc';
$needle = 'E';//判断是否包含a这个字符
$tmparray = explode($needle,$str);
4.用in_array检查数组中是否存在某个值
// bool in_array ( mixed $needle , array $haystack [, bool $strict = FALSE ] )
//in_array()例子
$os=array("Mac","NT","Irix","Linux");
if(in_array("Irix",$os)){
    echo "Got Irix";
}
if(in_array("mac",$os)){
    echo "Got mac";
}
//第二个条件失败，因为in_array()是区分大小写的 所以只输出Got Irix
//in_array() 严格类型检查例子
$a = array('1.10', 12.4, 1.13);
if (in_array('12.4', $a, true)) {
    echo "'12.4' found with strict check\n";
}
if (in_array(1.13, $a, true)) {
    echo "1.13 found with strict check\n";
}
//程序会输出1.13 found with strict check
//in_array()中数组作为needle
$a = array(array('p', 'h'), array('p', 'r'), 'o');
if (in_array(array('p', 'h'), $a)) {
    echo "'ph' was found\n";
}
if (in_array(array('f', 'i'), $a)) {
    echo "'fi' was found\n";
}
if (in_array('o', $a)) {
    echo "'o' was found\n";
}
//程序会输出
//'ph' was found
//'o' was found