How to Overwrite Default Arguments in PHP Functions?

Using Default Arguments in a Function

When creating PHP functions, you can specify default values for arguments to provide flexibility and reduce the need for explicit assignment. However, setting different arguments for parameters later in the function declaration can sometimes be confusing.

Consider the following function:

<code class="php">function foo($blah, $x = "some value", $y = "some other value") {
    // code here!
}</code>

To use the default argument for $x and set a different value for $y, simply pass null for $x as follows:

<code class="php">foo("blah", null, "test");</code>

This assigns the default value "some value" to $x while overriding the default for $y.

However, attempting to set $x by its variable name (e.g., foo("blah", $x, $y = "test")) will not work as expected. This is because default arguments can only be applied to the last parameters in the function definition.

To address this limitation and allow for a more dynamic argument handling, you can modify the function declaration as such:

<code class="php">function foo($blah, $x = null, $y = null) {
    if (null === $x) {
        $x = "some value";
    }

    if (null === $y) {
        $y = "some other value";
    }

    // code here!
}</code>

With this approach, you can pass null values for specific parameters to use their default values while overriding others like so:

<code class="php">foo("blah", null, "non-default y value");</code>

In this example, $x will receive its default value while $y will be assigned the specified non-default value.

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