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22. Function Syntax

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PHP(2015-10)
============

Functions wouldn't be nearly as useful if they weren't able to take in some input. This is where **parameters** or**arguments** come in. These are the variables or inputs that a function uses to perform calculations.

```
<pre style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(197, 200, 198); border-radius: 2px; padding: 7px 10px; font-size: 15px; line-height: 22px; background-color: rgb(35, 44, 49);">
```
<span class="keyword" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(178, 148, 187);"><span class="keyword" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);">function</span></span> squareValue(<span class="variable" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(181, 137, 0);"><span class="variable" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);">$number</span></span>) {
  <span class="keyword" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(178, 148, 187);"><span class="keyword" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);">echo</span></span> <span class="variable" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(181, 137, 0);"><span class="variable" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);">$number</span></span> * <span class="variable" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(181, 137, 0);"><span class="variable" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);">$number</span></span>;
}

<span class="variable" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(181, 137, 0);"><span class="variable" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);">$n</span></span> = <span class="number" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(222, 147, 95);"><span class="number" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);">6</span></span>;
squareValue(<span class="variable" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(181, 137, 0);"><span class="variable" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);">$n</span></span>); <span class="comment" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0); color: rgb(150, 152, 150); font-style: italic;"><span class="comment" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);">// echos 36</span></span>

```
```

The function `squareValue`, above, takes one parameter, which it multiplies by itself and then echos the result. The names of the parameters themselves are used internally within the function, so they should be named something helpful.

You can also use multiple parameters as long as they are separated by commas.

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