如何从PHP的关联数组中删除具有空键的值？

Question

I have a key that appears to be an empty string, however using unset($array[""]); does not remove the key/value pair. I don't see another function that does what I want, so I'm guessing it's more complicated that just calling a function.

The line for the element on a print_r is [] => 1 , which indicates to me that the key is the empty string.

Using var_export, the element is listed as '' => 1 .

Using var_dump, the element is listed as [""]=>int(1) .

So far, I have tried all of the suggested methods of removal, but none have removed the element. I have tried unset($array[""]); , unset($array['']); , and unset($array[null]); with no luck.

Answer 1

Try unset($array[null]);

If that doesn't work, print the array via var_export or var_dump instead of print_r , since this allows you to see the type of the key. Use var_export to see the data in PHP syntax.

var_export($array);

Note that var_export does not work with recursive structures.

Answer 2

Tried:

$someList = Array('A' => 'Foo', 'B' => 'Bar', '' => 'Bah');
print_r($someList);
echo '<br/>';
unset($someList['A']);
print_r($someList);
echo '<br/>';
unset($someList['']);
print_r($someList);
echo '<br/>';

Got:

Array ( [A] => Foo [B] => Bar [] => Bah )
Array ( [B] => Bar [] => Bah )
Array ( [B] => Bar )

You should analyse where the key come from, too...

Answer 3

My guess is that it's not an empty string. Try the following to see what you get:

foreach ($array as $index => $value) {
    echo $index;
    echo ' is ';
    echo gettype($index);
    echo "\n";
}

Answer 4

Try using var_dump instead of print_r . This may give you a better idea of what exactly the key is.

Answer 5

Not sure what to tell you. Running this script

<?php

$arr = array(
        false   => 1
    ,   true    => 2
    ,   null    => 3
    ,   'test'  => 4
//  ,   ''      => 5
);

print_r( $arr );

foreach ( $arr as $key => $value )
{
    var_dump( $key );
}

unset( $arr[''] );

print_r( $arr );

I get the following output

Array
(
    [0] => 1
    [1] => 2
    [] => 3
    [test] => 4
)
int(0)
int(1)
string(0) ""
string(4) "test"
Array
(
    [0] => 1
    [1] => 2
    [test] => 4
)

See how the "null" array key was type converted to an empty string?

Are you sure you are not working with a copy of the array? If you did this call to unset() from inside a function, it's possible that you are.

This was tested on PHP 5.2.0

Answer 6

Please post the code you use to remove the element as well your checker code before and after that line.

What I'm looking for is something like this:

var_export($array);
echo "\n";
unset($array[""]);
var_export($array);

Please also post the complete output of both var_export lines.

I'm looking for something like this:

array (
  '' => 1,
)
array (
)