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84 lines
2.7 KiB
Markdown
84 lines
2.7 KiB
Markdown
When writing code, there will be times when you need to perform actions only under certain circumstances.
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There are several ways to control execution in PHP.
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We will start with an if statement.
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```php
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<?php
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$animal = 'cow';
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if ($animal == 'cow') {
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echo "Moooooo.....\n";
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}
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```
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All conditionals check to see if a statement evaluates to true or false.
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In the case above, since `$animal` equals 'cow', the statement returns true and the contents of the if statement are executed.
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An if statement can have multiple conditions chained together.
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If the first if statement returns false, then PHP will check each `elseif`.
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If none of the checks return true, then the else block will be executed.
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```php
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$animal = 'bird';
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if ($animal == 'dog') {
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echo "Woof! 🐶\n";
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} elseif ($animal == 'cat') {
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echo "Meow!? 🐱\n";
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} elseif ($animal == 'bird') {
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echo "Chirp! 🐦\n";
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} else {
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echo "I am not a dog, cat or bird\n";
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}
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```
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An alternative to the if statement is the switch.
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A switch statement has multiple cases to check if the value in parentheses equals something.
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In this statement, since `$food` equals 'apples', the switch will echo "Eating an apple".
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The default case will be run if no other case evaluates to true, like an else statement.
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```php
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$food = 'apples';
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switch ($food) {
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case 'apples':
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echo "Eating an apple\n";
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break;
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case 'oranges':
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echo "Eating an orange\n";
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break;
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case 'peaches':
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echo "Eating a peach\n";
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break;
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default:
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echo "No food, I am hungry\n";
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}
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```
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Breaks are a special keyword that tell PHP to stop execution once a case passes.
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If you do not use a break, PHP will continue to execute all following cases.
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In this switch, both "Drinking water" and "Drinking tea" will be executed since there is no break in the 'water' case.
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```php
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$drink = 'water';
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switch ($drink) {
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case 'water':
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echo "Drinking water\n";
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case 'tea':
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echo "Drinking tea\n";
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break;
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}
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```
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PHP also supports single line conditionals called a ternary.
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In a ternary, the condition is followed by a question mark before the value that should be returned if the condition is true and then another colon and a value to return if the condition is false.
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```php
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$language = 'english';
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echo $language == 'spanish' ? "hola\n" : "hello\n";
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```
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Lastly, there is another form of a ternary that checks if a value is set and then returns the value to the right of the two question marks if the value is null.
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```php
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echo $IDoNotExist ?? "Variable not set\n";
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```
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You can also chain multiple checks in a row.
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```php
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$IExist = "Variable exists\n";
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echo $IDoNotExist ?? $IExist ?? "Neither variable is set\n";
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```
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