Description:
------------
PHP 7.3.5 (cli) (built: May  8 2019 02:40:53) ( NTS )                        
Copyright (c) 1997-2018 The PHP Group                                        
Zend Engine v3.3.5, Copyright (c) 1998-2018 Zend Technologies                
    with Zend OPcache v7.3.5, Copyright (c) 1999-2018, by Zend Technologies  

root@90922e40286a:/usr/local/etc/php/conf.d# apt install php-ldap                                     
Reading package lists... Done                                                                         
Building dependency tree                                                                              
Reading state information... Done                                                                     
Package php-ldap is a virtual package provided by:                                                    
  php7.3-ldap 7.3.5-1+0~20190503093827.38+stretch~1.gbp60a41b [Not candidate version]                 
  php7.2-ldap 7.2.18-1+0~20190503103213.21+stretch~1.gbp101320 [Not candidate version]                
  php7.1-ldap 7.1.29-1+0~20190503101539.18+stretch~1.gbp946c98 [Not candidate version]                
  php7.0-ldap 7.0.33-7+0~20190503101027.13+stretch~1.gbp26f991 [Not candidate version]                
  php5.6-ldap 5.6.40-7+0~20190503101815.14+stretch~1.gbp1a44f9 [Not candidate version]                
  php7.3-ldap 7.3.4-2 [Not candidate version]                                                         
  php7.0-ldap 7.0.33-0+deb9u3 [Not candidate version]                                                 
                                                                                                      
E: Package 'php-ldap' has no installation candidate                                                   
root@90922e40286a:/usr/local/etc/php/conf.d# apt install php7.3-ldap                                  
Reading package lists... Done                                                                         
Building dependency tree                                                                              
Reading state information... Done                                                                     
Package php7.3-ldap is not available, but is referred to by another package.                          
This may mean that the package is missing, has been obsoleted, or                                     
is only available from another source                                                                 
                                                                                                      
E: Package 'php7.3-ldap' has no installation candidate                                                
root@90922e40286a:/usr/local/etc/php/conf.d# php -m                                                   
[PHP Modules]                                                                                         
Core                                                                                                  
ctype                                                                                                 
curl                                                                                                  
date                                                                                                  
dom                                                                                                   
fileinfo                                                                                              
filter                                                                                                
ftp                                                                                                   
gd                                                                                                    
hash                                                                                                  
iconv                                                                                                 
json                                                                                                  
libxml                                                                                                
mbstring                                                                                              
mysqli                                                                                                
mysqlnd                                                                                               
openssl                                                                                               
pcre                                                                                                  
PDO                                                                                                   
pdo_sqlite                                                                                            
Phar                                                                                                  
posix                                                                                                 
readline                                                                                              
Reflection                                                                                            
session                                                                                               
SimpleXML                                                                                             
sodium                                                                                                
SPL                                                                                                   
sqlite3                                                                                               
standard                                                                                              
tokenizer                                                                                             
xml                                                                                                   
xmlreader                                                                                             
xmlwriter                                                                                             
Zend OPcache                                                                                          
zip                                                                                                   
zlib                                                                                                  
                                                                                                      
[Zend Modules]                                                                                        
Zend OPcache                                                                                          
                                                                                                      

Expected result:
----------------
php7.3-ldap installed