PHP Learning Notes (a) array

　　methods for initializing arrays: Unified initialization or initialization by item.

　　Ways to iterate through an array:

1. For loop

2. Do ... While statement

3. While statement

4. foreach

foreach ($arras$key=$val)    {        echo$key. " =". $val. " <br/> ";    }

The key value in an array can be an integer or a string.

An array can store any data type.

Understanding content: Array Operators.

　Array sorting issues:

　　Internal sorting:

1. Bubble sort

2. Select the Sorting method

3. Insert Sort method

4. Fast sorting method

　　External sort:

Questions about function Parameters:

　　When the formal parameter takes the address: Indicates that the address is passed, and the address in the original array passes through, changing the original value.

When the parameter does not take address: The default pass is a value pass, not an address pass, which is a new array pass, and does not alter the value of the original array.

Other knowledge:

Common functions:

1. Count

Count ($arr);  // gets the length of the array

2, Is_array: Determine whether the array.

3. Print_r: Displays easy-to-understand information about a variable. If a string,integer , or floatis given, the variable value itself is printed. If an array is given , the keys and elements are displayed in a certain format. Object is similar to an array.

4. Var_dump: Returns the type and value of an expression.

5, Explode: Use one string to split another string.

6. Round: Rounding the specified number of digits for floating-point numbers.

7, unset: Destroy an element, you can also destroy a variable.

When a variable is destroyed in an array, the array is not automatically re-assembled, and the data corresponding to that key value in the array is undefined

8.How to turn off notice level tips in PHP:

1.php.ini file modified to: error_reporting = E_all & ~e_notice

2. Add code to the page where you want to suppress error prompts: error_reporting (e_all ^ e_notice);

PHP Learning Notes (a) array