How to modify constants in php

How to modify constants in php: You can use regular expressions to modify constants. To use regular expressions, we need to use the preg_replace() function, which is used to perform a regular expression search and replacement.

#We can use regular replacement to modify constants, which is the simplest and most convenient.

(Recommended tutorial: php tutorial)

Function introduction:

preg_replace function performs a regular expression search and replacement.

Function syntax:

mixed preg_replace(mixed $pattern , mixed $replacement, mixed $subject[, int $limit = -1[, int &$count]])

Parameter description:

• $pattern: The pattern to be searched, which can be a string or a string array.

• $replacement: String or array of strings used for replacement.

• $subject: The target string or string array to be searched and replaced.

• $limit: Optional, the maximum number of substitutions for each subject string per pattern. The default is -1 (no limit).

• $count: Optional, the number of times the replacement is performed.

Return value:

If subject is an array, preg_replace() returns an array, otherwise it returns a string. If a match is found, the replaced subject is returned, otherwise the unchanged subject is returned. If an error occurs, NULL is returned.

Code implementation:

/*
    @param 常量文件
    @param 修改数组(常量名=>常量值)
    @return 失败返回false  成功修改常量文件
    */
    function constEdit($file, $arr)
    {
        $info = file_get_contents($file);
        foreach ($arr as $k => $v) {
            $info = preg_replace("/define\(\"{$k}\",\".*?\"\)/", "define(\"{$k}\",\"{$v}\")", $info);
        }
        return file_put_contents($file, $info);
    }

Using this method we only need to pass in the corresponding constant file location and modified array.

Application scenario:

<form action="action.php" method="post">
    <input name="HOST" type="text" />
    <input name="DBNAME" type="text" />
    <input type="submit" value="修改"/>
</form>

At this time, in the action.php page, you only need to receive the complete array of $_POST and pass it into the method.

It should be noted that you need to use double quotes when defining constants, such as:

define("HOST","127.0.0.1");
define("DBNAME","mysql");

Secondly, the name of the constant should correspond to the name in the form.

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