Lecture 4: Built-In Functions & URLs

Overview: Covers essential PHP native functions for string and array manipulation, alongside understanding URL structures.

• String Built-In Functions:
  • strlen(): Returns the length of a string.
  • strpos(): Finds the position of the first occurrence of a substring.
  • substr(): Extracts and returns a part of a string.
  • str_replace(): Replaces occurrences of a specified search string with a replacement string.
  • strtolower(): Converts the entire string to lowercase.
  • strtoupper(): Converts the entire string to uppercase.
  • trim(): Removes whitespace (or other specified characters) from both ends of a string.
  • md5(): Calculates the MD5 hash of a string.
  • filter_var(): Filters a variable using a specified filter (e.g., validating an email).
• Array Built-In Functions:
  • count(): Counts the total number of elements in an array.
  • array_push(): Pushes one or more elements to the end of an array.
  • array_pop(): Pops (removes) the last element off the end of an array.
  • array_shift(): Shifts (removes) the first element off the beginning of an array.
  • array_unshift(): Prepends (adds) one or more elements to the beginning of an array.
  • array_merge(): Merges two or more arrays together.
  • array_reverse(): Reverses the order of the array's elements.
  • in_array(): Checks if a specific value exists inside an array.
• HTML Uniform Resource Locators (URL):
  • A URL is a web address used to locate documents or data on the web.
  • Structure: scheme://prefix.domain:port/path/filename
    • scheme: The internet service type (e.g., http or https).
    • prefix: The domain prefix (default is www).
    • domain: The internet domain name (e.g., w3schools.com).
    • port: Port number at the host (default for http is 80).
    • path: Path at the server (omitted path defaults to the root directory).
    • filename: Name of the specific document or resource.