array_unique showing error Array to string convers

Question

For getting the unique values i am using unique values. Below is the code i am using

array_unique($results_external);
aasort($results_external,"created_on");
$returns_buy_external[]=array_reverse($results_external, true);

If i use the code like this, below is the error i am getting

A PHP Error was encountered Severity: Notice

Message: Array to string conversion

Filename: models/product_model.php

Line Number: 3550

3550 line is array_unique($results_external);

Can anyone help me, why it is getting error like this and how to solve it?

results_external sample format coming is below

Array
(
    [0] => Array
        (
            [id] => 144
            [name] => test
            [slug] => test
            [images] => {"9eebd0f69772dd3bdf8c787864437c85":{"filename":"9eebd0f69772dd3bdf8c787864437c85.png","alt":"TRESemme Smooth and Shine","caption":""}}
            [track_stock] => 1
            [seo_title] => ttt
            [qty] => 0
            [product_type] => 0
            [price] => 0.00
            [saleprice] => 0.00
            [external_links] => http://test.com
            [external_price] => 285.00
            [external_saleprice] => 285.00
            [created_on] => 2013-11-08 15:03:24
        )
)

Answer 1

As per the docs, array_unique compares elements as strings by default. This means your 2D array is being converted to an array of strings (all being "Array" and generating the array-to-string Notice) or which only one can be returned as unique.

Use the SORT_REGULAR flag to compare the elements as they are, but be aware that arrays are only considered equal if they have the same key-value pairs.

Example:

print_r(array_unique($array, SORT_REGULAR));