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PHP Basics

PHP Code​

  • <?php CODE ?>: Tag around PHP code.
  • echo: Display information to the screen.
  • //: Creates a single line comment.
  • /* */: Multiline Comment.
  • $variable; and $variable = value;: Ways of establishing variables in PHP.
  • var_dump(): Returns the type of the variable.
  • +, -, *, /, **: Mathematical Operators.
  • +=, -=, *=, /=: Combined Operators.
  • \n: Newline.
  • \t: Tab.
  • .: Concatenate multiple strings/values together.
  • .=: Concatenates multiple values into a string using an assignment operator.
  • ==: Compare two variables regardless of type.
  • ===: Compares two variables but must be the same type.
  • if (condition) { }: An if statement in PHP.
  • else { }: An else statement in PHP.
  • elseif { }: Chains if statements in PHP.
  • getlastmod(): Get the last time that the page was modified.
  • include ‘rel path’: Include other PHP files into the webpage.

Getting Started with PHP​

  • One of the most widely used technologies.
  • First released in 1995.
  • PHP: Personal Homepage Tools now PHP Hyper-text Preprocessor.
  • Maintained by 10 developers and comes with many frameworks and packages.
  • No installation needed, comes preinstalled normally.
  • Can be embedded into HTML using code blocks.
  • Does not need to be compiled.
  • Server Side Language - code is processed on the web server. The user only receives HTML.
  • Will not see PHP code in browser when testing.

Intro to Workspaces and PHP Code​

  • PHP can also be used as a general scripting language.
  • Can be run in a CLI (Command Line Interface).
  • PHP Code is put into codeblocks.
  • <?php INSERT CODE HERE ?>: Code block.
  • echo: Command that displays information to the screen.
  • Each line ends with a semicolon.
  • PHP does not care about extra whitespace.
  • Spacing is still best practice for readability.

PHP Comments​

  • Comments allow you to make notes in code to make the code easier to read.
  • Can explain the how and why.
  • Comments allow for better organization.
  • Three types of comments:
    • Single Line: Created using two forward slashes //.
    • Multi Line: A single line can span multiple lines if no hard returns are used. Can also use multiple single line comments. For multi lines: Use a forward slash and an asterisk /* */.
    • Doc Block: Is used to give documentation for specific sections of code or the entire file. Should include author, summary, version, and license. Created using /* and ends with */ but each line has a space and an asterisk.

Variables in PHP​

  • Two parts of Code:
    • Retrieval and storage of data.
    • Logic of what to do with data and when.
  • Variables are boxes for data, it can change shape or form, but it is the same variable.
  • Variables are identified by their own unique name.
  • Always begin with a $ in PHP.
  • Variables cannot be started with a number.
  • Can be created empty by just putting the semicolon.
  • A value can be established using the = sign.
  • 4 Scalar variable types are supported in PHP:
    • Bool
    • Int
    • Floats
    • Strings
  • There are also arrays and objects in PHP.
  • A variable reference must also have the $ sign.

Integers​

  • Integers are whole numbers 1 - 9 and can be negative.
  • var_dump(): Prints in the output what a variable is and its type.
  • Supports all the normal operators. (+, -, *, /)

Floats​

  • Keep track of fractional and decimal values.
  • Normally used to keep track of distance or currency.
  • Supports the basic operators.
  • A floating point will return a float type if it is used in any operator.

Arithmetic Operators​

  • Anything that takes two or more values and returns one value. Normally are the math operators.
  • * is the multiplication operator.
  • / is the division operator.
  • The operators will return the type that is needed for the result of the operation.
  • ++ is the incrementing operator. Will add one to a value.
  • - is the decrementing operator. Will subtract one from a value.
  • If these operators are before the variable, they will return the result in the same call. If they are after, they will not return the operated results.
  • Also supports combined operators: (+=, -=, *=, /=).

Creating a simple Unit Conversion Tool​

  • echo: Outputs information all on the same line.

Strings​

  • A string is a series of characters specified between single or double quotations.
  • Single quotes strings represent each character in the string.
  • Double quoted strings allow you to represent variables inside the string.
  • PHP adds/expands the variable in the string.

Escaped Sequences​

  • Escape Sequences allow you to put certain symbols in strings using a backslash.
  • Break out of the way PHP normally interprets strings.
  • Two types:
    • Backslashes with an alphanumeric character. Ex: \n: newline, \t: tab.
    • Backslashes with a symbol. Ex: \$.
  • You can display the other types of quotes if it is surrounded by the first type: 'This would show “double quotes”'.
  • Escape sequences are only used for double quotes except for \'.

Combining Strings​

  • Concatenation - Combining data into a string.
  • Two string operators for concatenation:
    • .: Adds 1 or more strings together.
    • .=: Adds the argument on the right to the variable on the left.
  • Statements can be combined using multiple lines, but it is not normally as readable as on one line.
  • If on multiple lines, start with the concatenation character.

Booleans​

  • Can either be true or false. Can take on no other values.
  • Not case sensitive when it comes to boolean values. Can either be true or True.
  • Should normally be lowercase.
  • Order of Operations: Top down.
  • We can test program conditions using an if statement.

Comparing Values​

  • Operators can also compare two values. These are called comparison operators.
  • Equal and Identical Comparers.
  • PHP is a weakly or loosely typed language. Types do not need to be specified.
  • PHP will juggle types to make them usable in more situations.
  • Ex: Adding a string to an integer will result in an int type.
  • == compares two variables regardless of type.
  • === compares two variables but must be the same type.

Adding logic to programs​

  • Evaluating and taking actions with data is done by using conditional statements.
  • If statements are the simplest of these.
  • if (condition) { } is the syntax for an if statement.
  • An else statement will have the program do something if the if condition is not true.
  • else { }

Daily Exercise Program​

  • The date() function. Attribute is the way we want the date to be formatted.
  • ‘N’ is the day of the week.

HTML and PHP​

  • PHP was defined to be used to make web pages.
  • PHP can be added anywhere in an HTML file by using the PHP code tag.
  • The server needs to know that there is PHP in the file by changing the HTML extension to PHP.

Don’t Repeat Yourself​

  • Use PHP variables to change multiple elements throughout the code.
  • Useful when you need to use the same string multiple times.
  • You can use multiple PHP blocks throughout a webpage.
  • You only see HTML in the inspect element, not the PHP code.

Let PHP Do the Work​

  • date() function allows you to pull the current date.
  • getlastmod(): Gets time of last page modification.

Combining Multiple Files with Includes​

  • PHP allows the inclusion of other files of codes while keeping them separate.
  • It allows for better organization.
  • Allows for less repetition.
  • Files that are included in the webpage are normally in a file called inc.
  • include ‘rel path’: In PHP, to control the output of PHP echos, HTML tags can be included in the PHP string to control the output.