A generator is a special type of Iterator [→] that produces results more progressively instead of all at once. It produces values on the fly as they are needed, potentially saving memory and resources compared to generating an entire sequence upfront.
Here's an example of a generator in PHP:
01: function myGenerator() {
02: yield 1;
03: yield 2;
04: yield 3;
05: }
06:
07: // Using the generator to iterate over its values
08: $gen = myGenerator();
09: foreach ($gen as $value) {
10: echo $value . PHP_EOL;
11: }In this example:
- The
myGenerator()function is defined as a generator using theyieldkeyword. - Each
yieldstatement within the function produces a value for the generator. - The
$genvariable is assigned the generator object returned bymyGenerator(). - The
foreachloop iterates over the values generated by$gen, printing each value.
When myGenerator() is called, it doesn't execute the code inside the function immediately. Instead, it returns an iterator object that can be iterated over. Each time the foreach loop requests the next value from the generator, the function is executed until it reaches a yield statement, producing the next value in the sequence. This allows for the lazy evaluation of the sequence of values.
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