What is causing the syntax error in the PHP code provided in the forum thread?

The syntax error in the PHP code provided in the forum thread is caused by missing semicolons at the end of each line inside the array declaration. To solve this issue, simply add semicolons at the end of each line within the array declaration.

// Incorrect code with missing semicolons
$array = [
    'key1' => 'value1',
    'key2' => 'value2'
];

// Corrected code with semicolons added
$array = [
    'key1' => 'value1',
    'key2' => 'value2',
];