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Test of mb_internal_encoding()

Example #1 : test success
Example #2 : test success
Example #1
$input = [
]
$expected_output = $test_output
$test_output = [
  
'result' => [
    
'mixed' => 'UTF-8',
  ],
  
'php_version' => '7.1.30 Linux x86_64',
]
Example #2
$input = 'UTF-8'
$expected_output = $test_output
$test_output = [
  
'result' => [
    
'mixed' => true,
  ],
  
'php_version' => '7.1.30 Linux x86_64',
]