foreach loop - php - weird behavior [duplicate] - php

Question

This question already has answers here:
PHP Foreach Pass by Reference: Last Element Duplicating? (Bug?) [duplicate]
(6 answers)
Closed 8 years ago.
I am new to PHP and I am experimenting
right now with some foreach loops in PHP.
I know that it is recommended to unset
the foreach loop variables after the loop.
I noticed that if I include the lines // 1 // and
// 2 //, this script prints the right thing.
...
Name: Rachel, Age: 56
Name: Grace, Age: 44
( It also prints the right thing if in the last loop, I use other
variable names like $n and $a instead of $name and $age.)
But if I comment lines // 1 // and // 2 // out, it prints:
Name: Lisa, Age: 28
Name: Jack, Age: 16
Name: Ryan, Age: 35
Name: Rachel, Age: 46
Name: Grace, Age: 34
Name: Lisa, Age: 38
Name: Jack, Age: 26
Name: Ryan, Age: 45
Name: Rachel, Age: 56
Name: Grace, Age: 56
Notice that 56 is printed two times.
Why does it behave that way?
I mean: what happens under the hood?
<?php
$employee_age = array();
$employee_age["Lisa"] = "28";
$employee_age["Jack"] = "16";
$employee_age["Ryan"] = "35";
$employee_age["Rachel"] = "46";
$employee_age["Grace"] = "34";
foreach( $employee_age as $name => $age){
echo "Name: $name, Age: $age <br />";
}
echo "<br>";
unset($age);
unset($name);
foreach( $employee_age as $name => &$age){
$age += 10;
}
// echo "<br>";
// unset($age); // 1 //
// unset($name); // 2 //
foreach( $employee_age as $name => $age){
echo "Name: $name, Age: $age <br />";
}
echo "<br>";
unset($age);
unset($name);
?>

Answer 1

If you var_dump($employee_age) before the second loop you'll notice that the last entry say &int instead of int. It is still a reference. It points to the last element (ignoring itself). And that is Rachel with 56.
Look into the manual's warning: http://pl.php.net/manual/en/control-structures.foreach.php
Reference of a $value and the last array element remain even after the foreach loop. It is recommended to destroy it by unset().

Answer 2

It's PHP's behavior of a referenced item.
Reason : I think this guy can explain better than me.
Just a little memo.
Alternatively, to fix this, you can add & to $age at your third foreach:
foreach( $employee_age as $name => &$age){
echo "Name: $name, Age: $age <br />";
}

Answer 3

Hm.. not sure why you unset,
simpler:
$employee_age = array(
"Lisa" => 28,
"Jack" => 16,
"Ryan" => 35,
"Rachel" => 46,
"Grace" => 34);
foreach( $employee_age as $name => $age){
echo "Name: $name, Age: $age <br />";
}
echo "<br>";
foreach( $employee_age as $name => $age){
$age2 = $age + 10; // (Don't think this is required)
echo "Name: $name, Age: $age2 <br />"; // Try with just $age+10
}
?>

Answer 4

Grace = 56 because your code is;
foreach( $employee_age as $name => &$age){
$age += 10;
}
Change it to
foreach( $employee_age as $name => $age){
$age += 10;
}
And Grace will 34 again.