&lt;?php$age = array&#40;&quot;Peter&quot;=&gt;&quot;35&quot;, &quot;Ben&quot;=&gt;&quot;37&quot;, &quot;Joe&quot;=&gt;&quot;43&quot;&#41;;print_r&#40;array_change_key_case&#40;$age, CASE_UPPER&#41;&#41;;?&gt;
A. Array ( [Peter] => 35 [Ben] => 37 [Joe] => 43 )
B. Array ( [peter] => 35 [ben] => 37 [joe] => 43 )
C. Array ( [PETER] => 35 [BEN] => 37 [JOE] => 43 )
D. Array ( [PeTeR] => 35 [BeN] => 37 [Joe] => 43 )
Answer:A
&lt;?php$age = array&#40;&quot;Peter&quot;=&gt;&quot;35&quot;, &quot;Ben&quot;=&gt;&quot;37&quot;, &quot;Joe&quot;=&gt;&quot;43&quot;&#41;;print_r&#40;array_change_key_case&#40;$age, CASE_UPPER&#41;&#41;;?&gt;
A. Array ( [Peter] => 35 [Ben] => 37 [Joe] => 43 ) B. Array ( [peter] => 35 [ben] => 37 [joe] => 43 ) C. Array ( [PETER] => 35 [BEN] => 37 [JOE] => 43 ) D. Array ( [PeTeR] => 35 [BeN] => 37 [Joe] => 43 )
Explanation: The array_change_key_case() function changes all keys in an array to lowercase or uppercase.