Single double quotation mark problem in PHP

Code Listing 1:

PHP$str = "我是一个php程序员";$length = strlen(preg_replace("/[\x00-\x7F]/", '', $str));echo $length;

Output 0 and prompt warning:preg_replace (): Null byte in regex in

Code Listing 2:

PHP$str = "我是一个php程序员";$length = strlen(preg_replace('/[\x00-\x7F]/', '', $str));echo $length;

Output 21

The only difference between the two codes is that the first argument of Preg_replace is a single or double quotation mark. Please explain!

Reply content:

Code Listing 1:

PHP$str = "我是一个php程序员";$length = strlen(preg_replace("/[\x00-\x7F]/", '', $str));echo $length;

Output 0 and prompt warning:preg_replace (): Null byte in regex in

Code Listing 2:

PHP$str = "我是一个php程序员";$length = strlen(preg_replace('/[\x00-\x7F]/', '', $str));echo $length;

Output 21

The only difference between the two codes is that the first argument of Preg_replace is a single or double quotation mark. Please explain!

Single quotation marks do not escape backslash \, double quotation marks will escape backslash \.

The first part is written as:
$str = "I am a PHP programmer";
$length = strlen (Preg_replace ("/[\\x00-\\x7f]/", "", $str));
Echo $length;

It won't be a problem.

and single double quotes do not matter, is your that ASCII \ No escape ... \ \ It's going to be.

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