如何重新定義 PHP 函數？

Redefining PHP Functions: Exploring the Options

In PHP, redefining a function is not as straightforward as rewriting it. Let's consider an example:

<code class="php">function this($a){
   return $a;
}</code>

If we attempt to redefine this function:

<code class="php">function this($a, $b){  //New this function
   return $a * $b;
}</code>

We encounter an error:

Fatal error: Cannot redeclare foo()

This is because PHP doesn't allow redefining existing functions. To overcome this, we can utilize the runkit extension:

Option 1: runkit_function_rename()

This function allows us to rename an existing function to a new name. For instance, we could rename the original this function to old_this:

<code class="php">runkit_function_rename('this', 'old_this');</code>

Now, we can create a new this function with the desired signature:

<code class="php">function this($a, $b){
   return $a * $b;
}</code>

Option 2: runkit_function_redefine()

This function allows us to modify the definition of an existing function:

<code class="php">runkit_function_redefine('this', '$a, $b', '$a * $b');</code>

Unlike runkit_function_rename(), this method preserves the original function name and overwrites its implementation.

By utilizing these runkit functions, we can effectively redefine PHP functions without encountering redefinition errors.

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