using array_diff on 2 arrays

[webdeveloper123]

Hi,

I have the following arrays:

$table = array ( 
            0 => array ( 
                'fname' => 'Peter', 
                'lname' => 'Smith', 
                'age' => '37'
                ), 
            1 => array ( 
                'fname' => 'Paul', 
                'lname' => 'Hartley', 
                'age' => '48'
                ), 
            2 => array ( 
                'fname' => 'Mary', 
                'lname' => 'Baker', 
                'age' => '42'
                ), 
            3 => array ( 
                'fname' => 'Jane', 
                'lname' => 'Doe', 
                'age' => '51'
              
                )
            );


$newdata = array ( 
            4 => array ( 
                'fname' => 'Paul', 
                'lname' => 'Hartley', 
                'age' => '48'
                ), 
            5 => array ( 
                'fname' => 'Mary', 
                'lname' => 'Baker', 
                'age' => '42'
                ), 
            6 => array ( 
                'fname' => 'Jane', 
                'lname' => 'Doe', 
                'age' => '51'
                ), 
            7 => array ( 
                'fname' => 'Toney', 
                'lname' => 'Brentford', 
                'age' => '25'
              
                )
            );

I am trying to use array_diff on the 2 arrays and based on my understanding only Peter Smith 37 should be returned. I am using this code:

$result = array_diff($table, $newdata);
print_r($result);

But I am getting same errors: (8 times)

 Array to string conversion in

Array ( )

Note the Array ( ) only shows once in the error.

On php.net it says array_diff is used in 1 dimensional arrays but you can: Of course you can check deeper dimensions by using:

array_diff($array1[0], $array2[0]);

So I did:

$result = array_diff($table[0], $newdata[0]);

From my understanding the number in the square bracket refers to the key in the array but I get this error:

Notice: Undefined offset: 0 in

Warning: array_diff(): Expected parameter 2 to be an array, null given 

I also used:

$result = array_diff($table[fname], $newdata[fname]);

But I get a whole host of errors

So I noticed that the examples in array_diff were all using the same key for multiple values, So Instead I tried array_diff_key:

$result = array_diff_key($table, $newdata);
print_r($result);

And I do get output, but not the expected output. This is the print_r($result) output

Array ( [0] => Array ( [fname] => Peter [lname] => Smith [age] => 37 ) [1] => Array ( [fname] => Paul [lname] => Hartley [age] => 48 ) [2] => Array ( [fname] => Mary [lname] => Baker [age] => 42 ) [3] => Array ( [fname] => Jane [lname] => Doe [age] => 51 ) )

but surely only Peter Smith 37 Should be the only output. Can anyone see where I'm going wrong?

Many thanks

[requinix]

array_diff will try to compare values like they were scalar values. For example, as strings. Thus the warnings about converting an array to a string. What you tried after that was throwing random code at the problem and hoping it would go away, which is inefficient and rarely ever works.

If you want a simple comparison between the values then use array_udiff() with a function that does a simple comparison - such as by using the <=> operator.

array_udiff($table, $newdata, fn($a, $b) => $a <=> $b)

 

[webdeveloper123]

sorry I didn't understand your code...is it missing function before fn? I tried it and then I tried:

print_r(fn($table, $newdata));

But I get error:

Parse error: syntax error, unexpected ')', expecting => (T_DOUBLE_ARROW) in

 

[gizmola]

He literally gave you code that works, only missing a semicolon:

$result = array_udiff($table, $newdata, fn($a, $b) => $a <=> $b);

var_dump($result);

If you are familiar with Javascript ES6, it is a similar type of anonymous function shorthand, equivalent to this:

$result = array_udiff($table, $newdata, function($a, $b) { return $a <=> $b; });

You need to have a current supported PHP version ( >= 7.4) although the syntax I showed works with any version 7.x or >

The "arrow function" version was introduced with php 7.4

[webdeveloper123]

thanks guys!