Some common PHP array errors and their solutions

In PHP, arrays are a very commonly used data structure. However, when we use arrays, we sometimes encounter some errors. This article will introduce some common PHP array errors and their solutions.

1. Undefined index

Personally, I think this is the most common PHP array error. This error message means that in PHP we try to use an array index that does not exist. The following is an example:

$my_array = array('apple', 'banana', 'orange');
echo $my_array[3];

The above code will return the following error message:

Notice: Undefined offset: 3

The offset here refers to the index value of the array, which is the subscript. The prompt says that "offset" is "undefined", which means that the index value asked here does not exist.

The solution is to print it and check whether the array subscript you are trying to access is correct. If the array subscript does exist, it may be caused by a case matching problem in the array key name or the array variable does not exist.

2. Undefined variable

This error is very close to Undefined index. The difference is that this error occurs when we use undefined variables. The following is an example:

echo $my_array[0];

The above code will return the following error message:

Notice: Undefined variable: my_array in <path_to_my_script></path_to_my_script>

This error message prompts that our $my_array variable is not defined. Therefore, the solution is to make sure that the variable is defined and try to open the variable.

3. Cannot use string offset as an array

This error occurs when we try to use string as an array. The following is an example:

$my_string = 'hello world';
echo $my_string[5]['test'];

The above code will return the following error message:

Warning: Illegal string offset 'test' in <path_to_my_script></path_to_my_script>

What this means is that $my_string[5] returns a character and is not an array, so you cannot use array subscripts on characters. The solution is to convert the string into an array and use the str_split() method of the string function.

4. Cannot use [] for reading

In PHP7.1, if you use [] to open an associative array, but the key is not If it exists, it will cause the following error message:

$my_array = ['apple' => 'good', 'banana' => 'better'];
echo $my_array['no_exist'];

This code will return the following error message:

PHP Fatal error:  Cannot use [] for reading in <path_to_my_script></path_to_my_script>

In PHP7.1, you cannot use [] to open a Associative array, but the key does not exist. The solution is also simple: use the isset() function to check whether the array subscript you want to use exists.

5. Illegal offset type

This error will occur if you try to use an illegal type as an array index. For example, the following code is illegal:

$my_array = array('apple', 'banana', 'orange');
$my_array[true] = 'good';

The above code will return the following error message:

Warning: Illegal offset type in <path_to_my_script></path_to_my_script>

The above code is illegal because true is not a legal Array subscript. The solution is to use legal array subscripts.

Summary

The above are common PHP array errors and their solutions. In the process of developing PHP code, don't worry when you encounter these errors. You only need to find the problem according to the error prompts and eliminate the errors.

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