You have an array $arr = ['a', 'b', 'a', 'c', 'b']. How can you create a new array where keys are unique values and values are their original first indexes?

hard📝 Application Q8 of 15

PHP - Array Functions

You have an array $arr = ['a', 'b', 'a', 'c', 'b']. How can you create a new array where keys are unique values and values are their original first indexes?

A$unique = array_unique($arr);

B$unique = array_unique(array_flip($arr));

C$unique = array_flip(array_unique($arr));

D$unique = array_flip($arr);

Step-by-Step Solution

Solution:

Step 1: Remove duplicates keeping first occurrences
array_unique($arr) removes duplicates, preserving first indexes.
Step 2: Flip keys and values to get unique values as keys and indexes as values
array_flip() swaps keys and values, so unique values become keys and their original indexes become values.
Final Answer:
$unique = array_flip(array_unique($arr)); -> Option C
Quick Check:
array_flip(array_unique()) = unique keys with original indexes [OK]

Quick Trick: Use array_flip(array_unique($arr)) for unique keys with original indexes [OK]

Common Mistakes:

Flipping before removing duplicates
Using only array_unique() without flipping
Flipping without removing duplicates

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You have an array $arr = ['a', 'b', 'a', 'c', 'b']. How can you create a new array where keys are unique values and values are their original first indexes?

Step 1: Remove duplicates keeping first occurrences

Step 2: Flip keys and values to get unique values as keys and indexes as values

Final Answer:

Quick Check:

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