Strings
## Learning Objectives
- Master string creation and manipulation
- Understand heredoc and nowdoc syntax
- Learn string functions
- Work with regular expressions
## String Creation
### Quotes
```php
```
### Concatenation
```php
```
## Heredoc
### Basic Heredoc
```php
```
### Heredoc with Indentation
```php
HTML;
echo $html;
?>
```
### Nowdoc
```php
```
## String Functions
### Length and Count
```php
```
### Case Conversion
```php
```
### Trimming
```php
```
### Padding
```php
```
### Substrings
```php
```
### Finding and Replacing
```php
```
### Replace with Count
```php
```
### Replace Multiple
```php
"Hi",
"World" => "PHP"
];
$result = str_replace(array_keys($replacements), array_values($replacements), $str);
echo $result; // Hi, PHP!
?>
```
### Substring Count
```php
```
### Substring Compare
```php
0 if a > b, 0 if equal
?>
```
## String Formatting
### Explode and Implode
```php
```
### Split String
```php
```
### String to Array
```php
```
## Formatting Output
### Number Formatting
```php
```
### Money Formatting
```php
formatCurrency($price, 'USD'); // $1,234.56
?>
```
### sprintf
```php
```
### printf
```php
```
## Character Functions
### ASCII Conversion
```php
```
### Check Character Types
```php
```
## Regular Expressions
### preg_match()
```php
```
### preg_match_all()
```php
```
### preg_replace()
```php
```
### preg_split()
```php
```
### Pattern Modifiers
```php
```
## URL Strings
### urlencode/urldecode
```php
```
### Parse URL
```php
```
### Build Query String
```php
"Alice",
"age" => 25,
"city" => "Paris"
];
http_build_query($data);
// "name=Alice&age=25&city=Paris"
http_build_query($data, "", "&", PHP_QUERY_RFC3986);
// URL-encoded properly
?>
```
## JSON Strings
### Encode/Decode
```php
"Alice", "age" => 25];
$json = json_encode($data);
// '{"name":"Alice","age":25}'
$decoded = json_decode($json, true);
// ["name" => "Alice", "age" => 25]
?>
```
### JSON Options
```php
""];
json_encode($data, JSON_HEX_TAG); // Escapes HTML tags
json_encode($data, JSON_PRETTY_PRINT); // Formatted output
json_encode($data, JSON_UNESCAPED_UNICODE); // Unicode chars
json_encode($data, JSON_FORCE_OBJECT); // Always object
?>
```
## Summary
- Strings: single quotes (literal), double quotes (interpolated)
- Heredoc `<<Welcome
Hello, $name!
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