php array string key index - php

Question

I have the following code:
$a = array();
$b = array('a', 'b');
for($i=0; $i<3; $i++){
$a[] = array($b[$i] => array(1, 2, 3));
}
print_r($a);
I get the following result:
Array
(
[0] => Array
(
[a] => Array
(
[0] => 1
[1] => 2
[2] => 3
)
)
[1] => Array
(
[b] => Array
(
[0] => 1
[1] => 2
[1] => 3
)
)
)
This is what I'm trying to accomplish:
array (
'a' => array ( 1, 2, 3 )
'b' => array ( 1, 2, 3 )
)
What am I doing wrong? I don't want $a to add numeric elements, but rather contain a, b, c as the indexes. Any suggestions? Thanks

Answer 1

change the forloop to like this
for($i=0; $i<count($b); $i++){
$a[$b[$i]] =array(1, 2, 3);
}

Answer 2

You can do,
$a = array();
$b = array('a', 'b');
for($i=0; $i<3; $i++){
if(isset($b[$i])){
$a += array($b[$i] => array(1, 2, 3));
}
}
DEMO.

Answer 3

You can set the key for $a like so:
$a = array();
$b = array('a', 'b');
for($i=0; $i<count($b); $i++){
$a[$b[$i]] = array(1, 2, 3);
}
print_r($a);
Also, i changed your for loop to use count($b) as you where iterating 1 to many times with your hard coded 3

Answer 4

Try:
$a[$b[$i]] = array(1,2,3);

Answer 5

One more iteration..
$a = array();
$b = array('a', 'b');
for($i=0; $i<3; $i++){
$a[$b[$i]] = array(1, 2, 3);
}
print_r($a);

Answer 6

Let's check what you were doing wrong.
$a = array();
$b = array('a', 'b'); // Count of elements is 2
for($i=0; $i<3; $i++){ // this will loop 3 times assigning 0,1,2 to $i where. You only needed 0 and 1 for an array with 2 elements
$a[] = array($b[$i] => array(1, 2, 3)); // here you are adding a new element to $a without providing key. So it becomes a numeric indexed array.
}
Solution:
for($i=0; $i<count($b); $i++){ // you could use $i<2 as well however count($b) makes your code more dynamic and result won't be affected if no of elements in $b changes.
$a[$b[$i]] =array(1, 2, 3); // you put $b[$i] as key for $a which creates an associative array
}