Seven interesting PHP functions_javascript skills

PHP has many built-in functions, most of which are widely used by programmers. But there are also some functions hidden in the corners. This article will introduce to you 7 functions that are little known but very useful. Programmers who have never used it may wish to come and take a look.

1.highlight_string()
When you need to display PHP code in a website, the highlight_string() function becomes very useful. This function outputs or returns a syntax-highlighted version of the given PHP code, using the colors defined in the PHP syntax highlighter.
Example:

Copy code The code is as follows:

highlight_string(' ');
?>

2.str_word_count()
This function must pass a parameter and return the number of words according to the parameter type. As shown below:

Copy code The code is as follows:

$str = "How many words do I have?";
echo str_word_count($str); //Outputs 6
?>

3.levenshtein()
This function mainly returns the Levenshtein distance between two strings. Levenshtein distance, also known as edit distance, refers to the minimum number of edit operations required between two strings to convert one into the other. Permitted editing operations include replacing one character with another, inserting a character, and deleting a character. This function is useful for finding typos submitted by users.

Example:

Copy code The code is as follows:

$str1 = "carrot";
$str2 = "carrrott";
echo levenshtein($str1, $str2); //Outputs 2
?>

4.get_defined_vars()
This function returns a multidimensional array containing a list of all defined variables, including environment variables, server variables and user-defined variables.

Example:

Copy code The code is as follows:

print_r(get_defined_vars());

5.escapeshellcmd()
This function is used to escape special symbols in strings, which can prevent users from playing tricks to crack the server system. You can use this function with the exec() or system() functions, which can reduce the malicious destructive behavior of online users.

Example:

Copy code The code is as follows:

$command = './configure '.$_POST['configure_options'];
$escaped_command = escapeshellcmd($command);
system($escaped_command);
?>

6.checkdate()
This function can be used to check whether the date is valid, for example, the year ranges from 0 to 32767, the month ranges from 1 to December, and the day changes with the month and leap year.

Example:

Copy code The code is as follows:

var_dump(checkdate (12, 31, 2000));
var_dump(checkdate(2, 29, 2001));
//Output
//bool(true)
//bool(false)
?>

7.php_strip_whitespace()
This function can return the source code file with PHP comments and whitespace characters removed, which is useful for comparing the actual number of codes and the number of comments.

Example:

Copy code The code is as follows:

// PHP comment here
/*
* Another PHP comment
*/
echo php_strip_whitespace(__FILE__);
// Newlines are considered whitespace, and are removed too:
do_nothing();

//Try the output results by hand
echo php_strip_whitespace(__FILE__); do_nothing();
?>