PHP Generators The Yield Keyword
Example
A yield statement is similar to a return statement, except that instead of stopping execution of the function and returning, yield instead returns a Generator object and pauses execution of the generator function.
Here is an example of the range function, written as a generator:
function gen_one_to_three() {
for ($i = 1; $i <= 3; $i++) {
// Note that $i is preserved between yields.
yield $i;
}
}
You can see that this function returns a Generator object by inspecting the output of var_dump:
var_dump(gen_one_to_three())
# Outputs:
class Generator (0) {
}
Yielding Values
The Generator object can then be iterated over like an array.
foreach (gen_one_to_three() as $value) {
echo "$value\n";
}
The above example will output:
1
2
3
Yielding Values with Keys
In addition to yielding values, you can also yield key/value pairs.
function gen_one_to_three() {
$keys = ["first", "second", "third"];
for ($i = 1; $i <= 3; $i++) {
// Note that $i is preserved between yields.
yield $keys[$i - 1] => $i;
}
}
foreach (gen_one_to_three() as $key => $value) {
echo "$key: $value\n";
}
The above example will output:
first: 1
second: 2
third: 3
