字串函數庫-搜尋類型_PHP

相容：(PHP 3, PHP 4, PHP 5)
strpos -- Find position of first occurrence of a string
尋找字元在字串第一次出現的位置
文法：int strpos ( string haystack, mixed needle [, int offset] )
傳回值：整數
函數種類: 資料處理

內容說明：
英文：
Returns the numeric position of the first occurrence of needle in the haystack string. Unlike the strrpos(), this function can take a full string as the needle parameter and the entire string will be used.
If needle is not found, strpos() will return boolean FALSE.

If needle is not a string, it is converted to an integer and applied as the ordinal value of a character.
The optional offset parameter allows you to specify which character in haystack to start searching. The position returned is still relative to the beginning of haystack.

中文：
傳回參數 needle在字串 haystack中第一次出現的位置，以數字表示。不像strrpos( )，此函式可以取參數 needle全部的字串，而且會使用全部的字串。如果找不到參數 needle，則傳回 false。

如果參數 needle不是字串時，它會轉換成整數並且按照字元的順序值來使用。
參數 offset允許你去指定在 haystack中從那一個字元開始搜尋，傳回的位置依然是相對於 haystack的起點。

*值得注意的是 needle 只能是一個字元，中文字等就不適合了。

例子講解：

$mystring = 'abc';

$findme= 'a';

$pos = strpos($mystring, $findme);



// Note our use of ===.Simply == would not work as expected

// because the position of 'a' was the 0th (first) character.

if ($pos === false) {

echo "The string '$findme' was not found in the string '$mystring'\";

} else {

echo \"The string '$findme' was found in the string '$mystring'\";

echo \" and exists at position $pos\";

}



// We can search for the character, ignoring anything before the offset

$newstring = 'abcdef abcdef';

$pos = strpos($newstring, 'a', 1); // $pos = 7, not 0

?>
strpos()與substr_count()對比：

$mystring = "Hello Chris\";

if (substr_count($mystring, \"Hello\") == 0)

echo \"no\";

// same as:

if (strpos($mystring, \"Hello\") === false)

echo \"no\";

?>

對比下面兩個代碼注意數字情況下，容易出現的錯誤，數字整數情況下不能看成字串。

$val1=123;

$val2="123,456,789\";

if (strpos($val2, $val1)!==false) echo \"matched\";

else echo \"not matched\";

?>
結果為： not matched


$val1=(string)123;

$val2="123,456,789\";

if (strpos($val2, $val1)!==false) echo \"matched\";

else echo \"not matched\";

?>
結果為：not matched

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