In PHP, variables are assigned values with the assignment operator (=). The same variable can later be reassigned a new value using the same operator.

This process is known as reassignment.

In PHP, if you want to join two strings together, you need to use the . operator.

This process is called concatenation. Put the . operator between the two strings in order to join them.

Note that strings are joined as-is, without inserting a whitespace character. So if you need to put spaces, you need to incorporate the whitespace manually within the string.

In PHP, there is a shortcut for appending a new string to the end of another string. This can be easily done with the string concatenation assignment operator (.=).

This operator will append the value on its right to the value on its left and then reassign the result to the variable on its left.

In PHP, a string is a sequence of characters surrounded by double quotation marks. It can be as long as you want and contain any letters, numbers, symbols, and spaces.

In PHP, sometimes special characters must be escaped in order to include them in a string. Escape sequences start with a backslash character (\).

There are a variety of escape sequences that can be used to accomplish different tasks. For example, to include a new line within a string, the sequence \n can be used. To include double quotation marks, the sequence \" can be used. Similarly, to include single quotes, the sequence \' can be used.

In PHP, when an assignment takes place, operations to the right of the assignment operator (=) will be evaluated to a single value first. The result of these operations will then be assigned to the variable.

In PHP, variables are assigned values with the assignment operator (=).

Variable names can contain numbers, letters, and underscores (_). A sigil ($) must always precede a variable name. They cannot start with a number and they cannot have spaces or any special characters.

The convention in PHP is to use snake case for variable naming; this means that lowercase words are delimited with an underscore character (_). Variable names are case-sensitive.

In PHP, the reference assignment operator (=&) is used to create a new variable as an alias to an existing spot in memory.

In other words, the reference assignment operator (=&) creates two variable names which point to the same value. So, changes to one variable will affect the other, without having to copy the existing data.

PHP supports integer values for numbers.

Integers are the set of all whole numbers, their negative counterparts, and zero. In other words, an integer is a number of the set ℤ = {…, -2, -1, 0, 1, 2, …}.

PHP supports an arithmetic operator for exponentiation (**).

This operator gives the result of raising the value on the left to the power of the value on the right.

PHP supports arithmetic operators for addition (+), subtraction (-), multiplication (*), and division (/).

PHP operators will return integers whenever the result of an operation evaluates to a whole number. If the result evaluates to a fraction or decimal, then it will return a floating point number.

PHP supports a modulo operator (%). The modulo operator returns the remainder of the left operand divided by the right operand. Operands of a modulo operation are converted to integers prior to performing the operation. The operation returns an integer with the same sign as the dividend.

PHP supports floating-point (decimal) numbers. They can be used to represent fractional quantities as well as precise measurements. Some examples of floating point numbers are 1.5, 4.231, 2.0, etc.